PROSPECTUS SUPPLEMENT (TO PROSPECTUS DATED AUGUST 5, 1996)

                        MASTEC, INC.
                              
                        Common Stock

     This Prospectus Supplement is being furnished to
Harrison-Wright Company, Incorporated, a North Carolina
corporation ("Harrison-Wright"), and to the holders of the
common stock, $1.00 par value (the "Harrison-Wright Common
Stock") and the preferred stock, $50.00 par value of
Harrison-Wright (the "Harrison-Wright Preferred Stock") (the
"Harrison-Wright Shareholders") in connection with the Asset
Purchase Agreement dated as of November 22, 1996 (the "Asset
Purchase Agreement"), entered into by and among Harrison-
Wright and its wholly-owned subsidiary Utility Precast,
Inc., a North Carolina corporation ("UPI") (Harrison-Wright
and UPI sometimes individually referred to as a "Seller" and
collectively referred to as the "Sellers") and  H-W
Acquisition I Co., Inc., a Delaware corporation ("H-W I"), H-
W Acquisition II Co., Inc., a Delaware corporation ("H-W
II") and H-W Acquisition III Co., Inc., a Delaware
corporation ("H-W III,") (H-W I, H-W II and H-W III
sometimes individually referred to as a "Buyer" and
collectively referred to as the "Buyers").  Each of the
Buyers is a newly-formed, indirect wholly-owned subsidiary
of MasTec, Inc., a Delaware corporation ("MasTec" or the
"Company").  A Prospectus Supplement dated November 15,
1996, a Prospectus Supplement dated November 7, 1996, the
Prospectus dated August 5, 1996 and copies of a draft dated
November 5, 1996 of the Asset Purchase Agreement were
previously distributed to the Harrison-Wright Shareholders.
    
      This Prospectus Supplement describes an Amendment
Agreement dated as of December 20 1996 (the "Amendment")
among the Sellers and Buyers which amends the terms of the
Asset Purchase Agreement.  See "Amendment to Terms of
Transaction." In addition, this Prospectus Supplement
includes a copy of the Amendment.



  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY
 THE SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURI-
     TIES COMMISSION NOR HAS THE COMMISSION OR ANY STATE
      SECURITIES COMMISSION PASSED UPON THE ACCURACY OR
      ADEQUACY OF THIS PROSPECTUS.  ANY REPRESENTATION
           TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this Prospectus Supplement is December 30, 1996.
                    
                    
                    AVAILABLE INFORMATION

     The Company is subject to the informational require
ments of the Securities Exchange Act of 1934, as amended
(the "Exchange Act"), and, in accordance therewith, files
reports, proxy statements and other information with the
Securities and Exchange Commission (the "Commission").  Such
reports, proxy statements and other information filed by the
Company can be inspected and copied at the public reference
facilities maintained by the Commission at Judiciary Plaza,
450 Fifth Street, N.W., Washington, D.C. 20549 and at the
following regional offices of the Commission: Seven World
Trade Center, Suite 1300, New York, New York 10048; and
Northwestern Atrium Center, 500 West Madison Street, Suite
1400, Chicago, Illinois 60661.  Copies of such material can
be obtained at prescribed rates by writing to the
Commission, Public Reference Section, 450 Fifth Street,
N.W., Washington, D.C. 20549.  The Common Stock is listed on
the Nasdaq National Market under the symbol "MASX."
Reports, proxy and information statements and other
information concerning the Company can also be inspected at
the Nasdaq National Market at 1735 17th Street, N.W.,
Washington, D.C. 20006.

     This Prospectus Supplement constitutes part of a
Registration Statement on Form S-4 (together with all
amendments and exhibits thereto, the "Registration
Statement") and does not contain all of the information set
forth in the Registration Statement, certain parts of which
have been omitted in accordance with the rules and
regulations of the Commission.  Pursuant to Rule 424(b) of
the Securities Act of 1933, as amended, this Prospectus
Supplement will be filed with the Commission electronically
via EDGAR.  For further information with respect to the
Company and the securities offered hereby, reference is made
to the Registration Statement, which includes the Prospectus
Supplement dated November 7, 1996, and to the exhibits and
schedules thereto.  Statements made in this Prospectus
Supplement as to the contents of any contract, agreement or
other document referred to are not necessarily complete.
With respect to each such contract, agreement or other
document filed as an exhibit to the Registration Statement,
reference is made to the exhibit for a more complete
description of the matter involved, and such statement is
qualified in its entirety by such reference.

            
                              2
            
            
            
            AMENDMENT TO TERMS OF THE TRANSACTION

     The Amendment amends the Asset Purchase Agreement to
extend the Liquidation Period from December 16, 1996 to
February 14, 1997.  In addition, the Buyers agree to make
certain payments and the Sellers agree to deliver additional
shares of Common Stock of MasTec to the Sellers or the
Escrow Agent, as described in the Amendment.  A copy of the
Amendment is attached hereto.  The stockholders of the
Sellers should review the Amendment for a complete
description of the modifications to the Asset Purchase
Agreement.  (Capitalized terms used herein have the meanings
given to them in the Asset Purchase Agreement and the
Amendment unless otherwise defined herein.)























                               3



NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO
MAKE ANY REPRESENTATIONS OTHER THAN THOSE CONTAINED IN THIS
PROSPECTUS IN CONNECTION WITH THE OFFERING MADE HEREBY, AND,
IF GIVEN OR MADE, SUCH INFORMATION OR REPRESENTATIONS MUST
NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED BY THE COMPANY.
THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL OR A
SOLICITATION OF AN OFFER TO BUY ANY SECURITIES OTHER THAN
THE SHARES OF COMMON STOCK OFFERED HEREBY OR AN OFFER TO
SELL OR A SOLICITATION OF AN OFFER TO BUY SUCH SHARES TO ANY
PERSON, OR THE SOLICITATION OF A PROXY FROM ANY PERSON, IN
ANY JURISDICTION IN WHICH SUCH OFFER, SOLICITATION OF AN
OFFER OR PROXY SOLICITATION IS UNLAWFUL.  THE DELIVERY OF
THIS PROSPECTUS AT ANY TIME DOES NOT IMPLY THAT THE
INFORMATION HEREIN IS CORRECT AS OF ANY TIME SUBSEQUENT TO
ITS DATE.



                      TABLE OF CONTENTS
                              
                                                        Page
Available Information                                    2
Proposed Change in Terms of the Transaction              3
Annex A:  Amendment Agreement
                              














                             4


                     AMENDMENT AGREEMENT
                              
                              
     THIS AMENDMENT AGREEMENT (the "Agreement") is made and
entered into as of the 20th day of December, 1996 by and
among H-W LIQUIDATING COMPANY, INC. ("H-W"); UPI LIQUIDATING
COMPANY, INC. ("UPI"); H-W ACQUISITION I CO., INC., H-W
ACQUISITION II CO., INC. and H-W ACQUISITION III CO., INC.
(collectively, "Purchasers"); MASTEC, INC. ("MasTec"); and
FIRST UNION NATIONAL BANK OF NORTH CAROLINA ("Escrow
Agent").

                    Statement of Purpose
                              
     H-W, UPI and Purchasers entered into an Asset Purchase
Agreement dated November 22, 1996 (the "Asset Purchase
Agreement") pursuant to which Purchasers purchased
substantially all of the assets, and assumed certain
liabilities, of H-W and UPI.  Capitalized terms in this
Agreement shall have the meaning given to them under the
Asset Purchase Agreement unless otherwise expressly defined
herein.

     Pursuant to the Asset Purchase Agreement, Purchasers
delivered shares of MasTec Common Stock in consideration for
the Acquired Assets and for the discharge of certain
liabilities that would have otherwise been assumed by
Purchasers.  Certain of such shares were delivered to H-W
and UPI directly, and the remaining shares were delivered to
Escrow Agent to be held and disbursed pursuant to the terms
of an Escrow Agreement dated November 22, 1996 by and among
H-W, UPI, Purchasers and Escrow Agent (the "Escrow
Agreement").  Pursuant to the Asset Purchase Agreement, all
such shares were to be sold in an orderly fashion during a
fifteen (15) trading day Liquidation Period ending on
December 16, 1996.  Purchasers' obligations under the Asset
Purchase Agreement are guaranteed by MasTec pursuant to a
Guaranty Agreement dated November 22, 1996 (the "Guaranty
Agreement").

     Purchasers now desire to extend the Liquidation Period
until the close of business on February 14, 1997.  The
parties desire to enter this Agreement to amend the Asset
Purchase Agreement, Escrow Agreement and Guaranty Agreement
to provide for such extension.

     NOW, THEREFORE, in consideration of the premises and
mutual covenants contained herein, the parties hereto hereby
agree that the Asset Purchase Agreement, Escrow Agreement
and Guaranty Agreement are amended as follows:

     1.   Extension of Liquidation Period.  The Liquidation
Period is hereby extended to the close of business on
February 14, 1997.

                             A-1


     2.   Increase in Purchase Price.

          (a)  The Purchase Price is hereby increased by the
sum of Three Hundred Thousand Four Hundred Eight Dollars
($300,408) as follows:

          (1)  Addition to Purchase  Price................... $165,000
          (2)  Lost cash tax savings (Deferred Comp).........  $45,055
          (3)  Interest through December 16 on Deferred Comp.   $8,126
          (4)  Lost deductions (Deferred Comp)...............  $82,227
                                                              ________
                                        TOTAL ............... $300,408
     
Provided, however, that such sum shall be reduced to One
Hundred Seventy-Three Thousand One Hundred Twenty-Six
Dollars ($173,126) (i.e., the total amount above reduced by
the aggregate amounts in items 2(a)(2) and 2(a)(4) above) in
the event that H-W has received on or before December 31,
1996 cash from the sale of Purchase Price Shares or
otherwise from Purchasers  (other than the payment described
in Paragraph 3 below) in an amount necessary for H-W to pay
all amounts due under the Deferred Compensation Plan
(including applicable payroll taxes), which amount is Nine
Hundred Forty-One Thousand Nine Hundred Twenty-One and
47/100 Dollars ($941,921.47).

          (b)  In addition to the amount in subparagraph (a)
above, the Purchase Price shall be increased by the
"Interest Adjustment" as hereinafter defined.  Beginning
December 16, 1996 and continuing thereafter until paid, the
principal sum of Six Million Four Hundred Thirty-Four
Thousand Seven Hundred Sixty-Seven and 39/100 Dollars
($6,434,767.39) of the Purchase Price shall accrue interest
on a daily basis at the rate of ten percent (10%) per annum.
Such principal sum shall be decreased dollar-for-dollar as
and when H-W, UPI and Escrow Agent receive cash proceeds
from the sale(s) of Purchase Price Shares or related
"Purchase Price Security Shares" (as defined in Paragraph 4
below) or otherwise receive cash payments from Purchasers
for the Purchase Price (but excluding for such purpose the
payment described in Paragraph 3 below).  For purposes of
this Agreement, the "Interest Adjustment" means the total
sum of such daily interest accruals.

          (c)  When used in this Agreement, the term
"Purchase Price" shall include the adjustments to the
Purchase Price set forth in this Paragraph 2.

     3.   Partial Cash Payment of Purchase Price.
Purchasers have paid H-W and UPI the total sum of Four
Hundred Thousand and No/100 Dollars ($400,000.00) as partial
payment for the Purchase Price, and H-W and UPI acknowledge
receipt of such payment.

                             A-2

     
     4.   Additional Purchase Price Shares.

          (a)  As of December 16, 1996, and as of each
Friday during the Liquidation Period thereafter (each a
"Determination Date"), H-W shall divide (i) the total
portion of the Purchase Price that H-W, UPI and Escrow Agent
have not received in cash as of such Determination Date
(either by direct cash payments by Purchasers to H-W and UPI
or by the receipt by H-W, UPI and Escrow Agent of net cash
proceeds from the sale of Purchase Price Shares or Purchase
Price Security Shares) by (ii) the closing price of MasTec
Common Stock on such Determination Date on the NASDAQ
national market system as reported on the NASDAQ composite
tape for such date (the "Closing Price").  The result is
referred to under this Agreement as the "Target Purchase
Price Shares."

          (b)   If the total number of Purchase Price Shares
and Purchase Price Security Shares held by H-W, UPI and
Escrow Agent as of a Determination Date is less than one
hundred ten percent (110%) of the number of Target Purchase
Price Shares as of such date, Purchasers shall deliver on
the next business day after the Determination Date
additional whole shares of MasTec Common Stock equal to such
difference (rounded up to the next highest whole number).
The additional shares delivered as of a Determination Date
shall be designated as either Purchase Price Shares or
"Purchase Price Security Shares" as follows: H-W shall
subtract (x) the total number of additional shares
previously delivered under this Paragraph 4 as Purchase
Price Security Shares from (y) ten percent (10%) of the
Target Purchase Price Shares as of the Determination Date.
The result (not less than zero) shall be delivered by
Purchasers as Purchase Price Security Shares to Escrow Agent
in the name of Escrow Agent for the benefit of H-W and UPI.
Title to such Purchase Price Security Shares shall not be
deemed to pass to H-W and UPI until such time as such shares
are required to be sold in accordance with the provisions of
subparagraph (d) below.  The remaining additional shares
calculated as of the Determination Date shall be Purchase
Price Shares and shall be delivered by Purchasers to H-W and
UPI (or at H-W's instruction, to H-W's and UPI's broker);
provided, however, that if Purchasers determine that the
total Purchase Price Shares held by Escrow Agent have an
aggregate value as of a Determination Date (based on the
Closing Price of MasTec Common Stock on such Determination
Date) that is less than Five Hundred Ninety Thousand Five
Hundred Dollars ($590,500) (minus any disbursements made to
Purchasers from the Escrow in accordance with the Escrow
Agreement prior to such Determination Date and ignoring any
portion of the Escrow related to Discharged Liabilities)
(the "Escrow Amount"), then Purchasers shall have the right
to cause a portion (as determined below) of the additional
Purchase Price Shares calculated as of the Determination
Date to be delivered to Escrow Agent to be held as part of
the Escrow and disbursed in accordance with the provisions
of Sections 3(a) - (d) of the Escrow Agreement.  The portion
of the additional Purchase Price Shares that Purchasers may
cause to be delivered to Escrow Agent is the number of such
shares that Purchasers reasonably determine to be necessary
to provide Escrow Agent with a sufficient number of total
Purchase Price Shares such that Escrow Agent will receive
net cash proceeds from the sale of such shares equal to the
Escrow Amount.

                            A-3


          (c)  H-W may cause additional Purchase Price
Shares and Purchase Price Security Shares to be calculated
other than as of a Determination Date and delivered on the
next business day by Purchasers if on a date between
Determination Dates the total number of  Purchase Price
Shares and Purchase Price Security Shares held as of such
date is less than the Target Purchase Price Shares
determined as of such date.

          (d)  As previously instructed, the broker for H-W
and UPI and Escrow Agent shall continue to sell Purchase
Price Shares during the Liquidation Period.  If H-W and UPI
notify such broker and Escrow Agent that total net sales
proceeds realized from the sale of Purchase Price Shares
during the Liquidation Period through a given date equals or
exceeds the total Purchase Price as of such date, then, as
instructed by H-W and UPI pursuant to such notice, no
additional Purchase Price Shares shall be sold and all
unsold Purchase Price Shares and Purchase Price Security
Shares shall be returned to Purchasers, together with any
surplus net cash proceeds as provided in subparagraph (f)
below.  Escrow Agent shall sell Purchase Price Security
Shares only upon the instruction of H-W and UPI after all
Purchase Price Shares have been sold if the net cash
proceeds realized from such sales of Purchase Price Shares
is less than the total Purchase Price and only to the extent
necessary to ensure that H-W, UPI and Escrow Agent receive
aggregate net cash proceeds from all sales of Purchase Price
Shares and Purchase Price Security Shares equal to the total
Purchase Price.  After the total Purchase Price has been
received in cash, H-W and UPI shall direct Escrow Agent to
return any unsold Purchase Price Security Shares to
Purchasers.    In addition, all net cash proceeds realized
from the sale of Purchase Price Security Shares shall be
disbursed by Escrow Agent to H-W and UPI pursuant to the
instruction of H-W and UPI, except for any surplus net cash
proceeds which shall be disbursed to Purchasers in
accordance with subparagraph (f) below.

          (e)  If at the end of the Liquidation Period H-W,
UPI and Escrow Agent have not received total net cash
proceeds realized from the sales of Purchase Price Shares
and  Purchase Price Security Shares, plus any cash paid
directly by Purchasers towards the Purchase Price, equal to
at least the total Purchase Price as of the last day of the
Liquidation Period, then Purchasers shall either (i)
repurchase on the first business day after the end of the
Liquidation Period any unsold Purchase Price Shares and (if
necessary) Purchase Price Security Shares at a price such
that H-W, UPI and Escrow Agent shall receive net cash
proceeds equal to such shortfall, or (ii) if all of the
Purchase Price Shares and Purchase Price Security Shares
have been sold, pay H-W, UPI and Escrow Agent in cash or
other immediately available funds on the first business day
after the Liquidation Period the amount of such shortfall;
provided, however, that after either such action Escrow
Agent shall have received the entire Escrow Amount (as
defined in Paragraph 4(b) above) in cash and H-W and UPI
shall have received the entire balance of the Purchase Price
in cash.

          (f)  If at the end of the Liquidation Period (or
such earlier date as of which the total Purchase Price has
been received in cash) H-W, UPI and Escrow Agent have
received total net cash proceeds realized from the sales of
Purchase Price Shares and Purchase Price Security Shares,
plus any cash paid directly by Purchasers towards the

                             A-4

Purchase Price, exceeding the total Purchase Price as of the
last day of the Liquidation Period (or such earlier date),
then H-W shall pay to Purchasers in cash or other
immediately available funds on the first business day after
the Liquidation Period (or such earlier date) the amount of
such excess.

          (g)  In the event Escrow Agent receives aggregate
net cash proceeds from the sale(s) of Purchase Price Shares
(including Purchase Price Shares delivered to Escrow Agent
in accordance with Paragraph 4(b) above) in excess of Five
Hundred Ninety Thousand Five Hundred Dollars ($590,500),
then H-W shall instruct Escrow Agent to disburse such excess
net cash proceeds to H-W and UPI; provided, however, that
any such excess net cash proceeds shall be returned to
Purchasers to the extent required by Paragraph 4(f) above.

          (h)  Schedule 1 attached to this Agreement
illustrates the calculation of additional Purchase Price
Shares under this paragraph 4 as of December 16, 1996.

     5.   Copeland Estate Note.  H-W previously made a
promissory note dated October 30, 1995 in the principal
amount of $512,000 to Lloyd Caudle, Executor Under Last Will
and Testament of Alex Copeland, Jr. (the "Copeland Estate
Note").  The Copeland Estate Note was one of the Assumed
Liabilities.  Effective as of December 16, 1996, the
Copeland Estate Note shall be removed as an Assumed
Liability and shall be added as a Discharged Liability.  If
Purchasers elect to pay in cash or other immediately
available funds all amounts due under the Deferred
Compensation Plan on or before December 31, 1996 in
accordance with Paragraph 2 above, then Purchasers shall
simultaneously pay the entire unpaid balance of the Copeland
Estate Note at such time.  If the Copeland Estate Note has
not been paid in full as of January 31, 1997 and an H-W has
not received sufficient cash proceeds from the sale of
Liability Discharge Shares through such date to pay such
amount, then Purchasers shall pay the entire unpaid balance
of the Copeland Estate Note as of such date.

     6.   Additional Liability Discharge Shares.

          (a)  As of December 16, 1996, and as of each other
Determination Date, H-W shall recalculate the Liability
Discharge Estimate (the "Revised Liability Discharge
Estimate").  H-W shall then divide (i) the Revised Liability
Discharge Estimate by (ii) the Closing Price of MasTec
Common Stock on such Determination Date.  The result is
referred to in this Agreement as the "Target Liability
Discharge Shares."  Attached to this Agreement is a revised
Schedule 1.3(c) to the Asset Purchase Agreement setting
forth the Discharged Liabilities as of December 16, 1996.

          (b)  If the total number of Liability Discharge
Shares and "Liability Discharge Security Shares" (as defined
below) held by Escrow Agent as of a Determination Date is
less than one hundred ten percent (110%) of the number of
Target Liability Discharge Shares as of such date,
Purchasers shall deliver on the next business day after the
Determination Date additional whole shares of MasTec Common Stock 

                             A-5


equal to such difference (rounded up to the next
highest whole number).  The additional shares delivered as
of a Determination Date shall be designated as either
Liability Discharge Shares or "Liability Discharge Security
Shares" as follows: H-W shall subtract (x) the total number
of additional shares previously delivered under this
Paragraph 6 as Liability Discharge Security Shares from (y)
ten percent (10%) of the Target Liability Discharge Shares
as of the Determination Date.  The result (not less than
zero) shall be delivered by Purchasers as Liability
Discharge Security Shares to Escrow Agent in the name of
Escrow Agent for the benefit of H-W and UPI.  Title to such
Liability Discharge Security Shares shall not be deemed to
pass to H-W and UPI until such time as such shares are
required to be sold in accordance with the provisions of
subparagraph (d) below.  The remaining additional shares
calculated as of the Determination Date shall be Liability
Discharge Shares and shall be delivered by Purchasers to
Escrow Agent.

          (c)  H-W may cause additional Liability Discharge
Shares and Liability Discharge Security Shares to be
calculated other than as of a Determination Date and
delivered on the next business day by Purchasers if on a
date between Determination Dates the total number of
Liability Discharge Shares and Liability Discharge Security
Shares held as of such date is less than the Target
Liability Discharge Shares determined as of such date.

          (d)  As previously instructed, Escrow Agent shall
continue to sell Liability Discharge Shares during the
Liquidation Period.  If H-W and UPI notify Escrow Agent that
all Discharged Liabilities have been fully satisfied during
the Liquidation Period, then, as instructed by H-W and UPI
pursuant to such notice, no additional Liability Discharge
Shares shall be sold and all unsold Liability Discharge
Shares and Liability Discharge Security Shares shall be
returned to Purchasers, together with any surplus net cash
proceeds as provided in subparagraph (f) below.  Escrow
Agent shall sell Liability Discharge Security Shares only
upon the instruction of H-W and UPI after all Liability
Discharge Shares have been sold if the net cash proceeds
realized from such sales of Liability Discharge Shares is
insufficient to fully satisfy the Discharged Liabilities and
only to the extent necessary to ensure that Escrow Agent
receives aggregate net cash proceeds from all sales of
Liability Discharge Shares and Liability Discharge Security
Shares sufficient to fully satisfy the Discharged
Liabilities.  Net cash proceeds realized from the sale of
Liability Discharge Security Shares shall be applied upon
the instruction of H-W and UPI solely towards the payment of
the Discharged Liabilities.  After the Discharged
Liabilities have been fully satisfied, H-W and UPI shall
direct Escrow Agent to (i) return any unsold Liability
Discharge Security Shares to Purchasers and (ii) disburse
any surplus net cash proceeds to Purchasers in accordance
with subparagraph (f) below.

          (e)  If at the end of the Liquidation Period
Escrow Agent has not received cash from Purchasers (either
directly or through the sale of Liability Discharge Shares
and Liability Discharge Security Shares) in an amount
sufficient to fully satisfy all of the Discharged
Liabilities, then Purchasers shall either (i) repurchase on
the first business day after the end of the Liquidation
Period any unsold Liability Discharge 

                             A-6


Shares and (if necessary) Liability Discharge Security Shares 
at a price such that Escrow Agent shall receive net cash proceeds 
equal to such shortfall, or (ii) if all of the Liability Discharge
Shares and Liability Discharge Security Shares have been
sold, pay the Escrow Agent in cash or other immediately
available funds on the first business day after the
Liquidation Period the amount of such shortfall.

          (f)  If at the end of the Liquidation Period (or
such earlier date as of which the Discharged Liabilities
have been fully satisfied), Escrow Agent has received total
net cash proceeds realized from the sales of Liability
Discharge Shares and Liability Discharge Security Shares,
plus any cash paid directly by Purchasers towards the
Discharged Liabilities, exceeding the total amount necessary
to fully satisfy the Discharged Liabilities, then H-W shall
instruct Escrow Agent to pay to Purchasers in cash or other
immediately available funds on the first business day after
the Liquidation Period (or such earlier date) the amount of
such excess.

          (g)  Schedule 2 attached to this Agreement
illustrates the calculation of additional Liability
Discharge Shares under this Paragraph 6 as of December 16,
1996.

     7.   Allocation of Shares.  Any shares of MasTec Common
Stock to be delivered in accordance with this Agreement
shall be allocated eighty percent (80%) to H-W and twenty
percent (20%) to UPI.

     8.   Operating Loss Allowance.  The maximum amount of
the Operating Loss Allowance set forth in Section 1.4(b)(iv)
of the Asset Purchase Agreement is increased to $222,261
(i.e., $148,928 plus $73,333).

     9.   Faison Preferred Stock.  Pursuant to a Stock
Redemption Agreement dated November 15, 1996 between H-W and
William W. Faison ("Faison"), H-W is obligated to pay Faison
the total purchase price for his shares of preferred stock
in H-W by no later than January 31, 1997.  The total
purchase price is Six Hundred Sixteen Thousand Five Hundred
Dollars ($616,500) plus accumulated and unpaid dividends.  H-
W estimates the total amount due as of January 31, 1997 will
be Six Hundred Nineteen Thousand Sixty-Nine Dollars
($619,069).  In the event H-W notifies Purchasers that H-W
has received insufficient net cash proceeds from the sale of
Purchase Price Shares to satisfy such obligation to Faison
by such date, Purchasers shall pay H-W in cash or other
immediately available funds prior to January 31, 1997 the
amount necessary to satisfy such obligation as set forth in
such notice, and such payment by Purchasers shall be
credited dollar-for-dollar against the Purchase Price.

     10.  Guaranty Agreement.  The obligations of MasTec
under the Guaranty Agreement shall apply with respect to
Purchasers' obligations under this Agreement.

     11.  Expense Reimbursement.  Purchasers and MasTec
shall reimburse H-W and UPI for all out-of-pocket expenses,
including without limitation reasonable attorneys' 

                             A-7

and accountants' fees, incurred by H-W and UPI in connection
with the negotiation and preparation of this Agreement.
     
     12.  Breach.   In the event Purchasers or MasTec breach
their obligations under the Asset Purchase Agreement,
Guaranty Agreement or this Agreement, then H-W and UPI, in
their sole discretion, may cause the immediate sale of all
shares of MasTec Common Stock held by H-W, UPI and Escrow
Agent (i.e., all Purchase Price Shares, Purchase Price
Security Shares, Liability Discharge Shares and Liability
Discharge Security Shares) and may pursue any and all other
legal or equitable remedies available to H-W and UPI.

     13.  Authorization.  H-W and UPI represent and warrant
to Purchasers and MasTec, and Purchasers and MasTec
represent and warrant to H-W and UPI, that this Agreement
has been duly authorized, that no further corporate action
is necessary for the execution and delivery of this
Agreement and that upon execution and delivery, this
Agreement shall be a valid, binding and enforceable
agreement.  H-W, UPI and Purchasers each agree that the
indemnification provisions of Section 8.2 of the Asset
Purchase Agreement shall apply with respect to this
Agreement, including without limitation with respect to the
foregoing representation and warranty and with respect to
any federal or state securities law claims related to the
shares of MasTec Common Stock to be delivered in accordance
with the terms of this Agreement.

     14.  Opinion of Counsel.  Purchasers and MasTec shall
cause their legal counsel to furnish to H-W and UPI the
legal opinion of such legal counsel, in a form reasonably
satisfactory to H-W and UPI, that (i) this Agreement has
been duly authorized and will be a valid, binding and
enforceable agreement and (ii) the delivery and sale of
MasTec Common Stock in accordance with this Agreement will
not violate federal or state securities laws.

     15.  Full Force and Effect.  Except as expressly or by
necessary implication amended hereby, the Asset Purchase
Agreement, Escrow Agreement and Guaranty Agreement shall
continue in full force and effect.

      16.   Amendment  or  Waiver.  This  Agreement  may  be
changed, waived, discharged or terminated only by a  writing
signed  by all of the parties hereto.  No delay or  omission
by  any  party  in exercising any right with respect  hereto
shall  operate  as  a waiver. A waiver on any  one  occasion
shall  not be construed as a bar to, or waiver of, any right
or remedy on any future occasion.

     17.  Severability.  To the extent any provision of this
Agreement is prohibited by or invalid under applicable  law,
such  provision shall be ineffective to the extent  of  such
prohibition   or   invalidity,  without   invalidating   the
remainder  of such provision or the remaining provisions  of
this Agreement.

                             A-8

      
      18.  Governing Law.  This Agreement shall be construed
and interpreted in accordance with the laws of the State  of
North Carolina.

      19.   Entire Agreement.  This Agreement, together with
the  Asset  Purchase  Agreement  and  the  other  agreements
contemplated  therein,  constitutes  the  entire   agreement
between  the  parties  relating  to  the  matters  described
herein.

     20.  Execution in Counterparts.  This Agreement and may
be  executed  in  two or more counterparts,  which  when  so
executed  shall  constitute one and the  same  agreement  or
direction.

      IN  WITNESS WHEREOF, the parties hereto have  executed
this Agreement as of the day and year first above written.

                              H-W LIQUIDATING COMPANY, INC.


                              By:   /s/ William M. Paris, Jr.
                                     William M. Paris, Jr.,
                                     President
                              
                              "H-W"


                              UPI LIQUIDATING COMPANY, INC.


                              By:   /s/ William M. Paris, Jr.
                                     William M. Paris, Jr.,
                                     Vice President
                              
                              "UPI"


                              H-W ACQUISITION I CO., INC.


                              By:  /s/ Jose M. Sariego
                                    Name:  Jose M. Sariego
                                    Title:  Vice President


                              H-W ACQUISITION II CO., INC.


                              By:  /s/ Jose M. Sariego
                                    Name:  Jose M. Sariego
                                    Title:  Vice President

                             A-9



                              H-W ACQUISITION III CO., INC.


                              By:  /s/ Jose M. Sareigo
                                    Name:  Jose M. Sariego
                                    Title:  Vice President

                              Collectively, "Purchasers"


                              MASTEC, INC.


                              By:  /s/ Jose M. Sareigo
                                    Name:  Jose M. Sariego
                                    Title:  Vice President

                              "MasTec"


Escrow Agent joins in the execution of this Agreement for
the limited purpose of  agreeing to the provisions of
Paragraph 4 and Paragraph 6 hereof only to the extent such
provisions modify the Escrow Agreement, and by executing
this Agreement the undersigned in no way becomes a party to
the Asset Purchase Agreement or the Guaranty Agreement.

                              FIRST UNION NATIONAL BANK OF
                                   NORTH CAROLINA


                              By:  /s/ Daniel J. Ober
                                    Name:  Daniel J. Ober
                                    Title:  Vice President

                              "Escrow Agent"











                             A-10



                         SCHEDULE 1
                              
  Illustration of Calculation of Additional Purchase Price
                           Shares
                   As of December 16, 1996
                              
                              
1.   Total Purchase Price not received in cash:

          $6,834,767.39 - $400,000 + $165,000 =  $6,599,767.39

2.   Divide amount in item 1 by $45.25 to get Target
     Purchase Price Shares:

          $6,599,767.39/$45.25 = 145,851.21
     
3.   Multiply number of shares in item 2 by 110% and round
     to next highest whole number:
     
          145,851.21 x 110% = 160,436.33 rounded to 160,437
     
4.   Subtract current Purchase Price Shares of 120,970 from
     amount in item 3:

     160,437 - 120,970 = 39,467

     This amount will be delivered as additional Purchase
     Price Shares and Purchase Price Security Shares.
     
5.   The number of shares in item 4 that are Purchase Price
     Security Shares is determined by subtracting 10% of the
     Target Purchase Price Shares (rounded up) by the number
     of shares previously received as Purchase Price
     Security Shares (which is 0 on this first Determination
     Date):

     14,585 - 0 = 14,585

6.   The number of shares in item 4 that are Purchase Price
     Shares is determined by subtracting the number of
     Purchase Price Security Shares in item 5 from the total
     additional shares in item 4:

     39,467 - 14,585 = 24,882
                         
                             A-11

                         
                         SCHEDULE 2
                              
     Illustration of Calculation of Additional Liability
                      Discharge Shares
                   As of December 16, 1996
                              
                              
1.   Revised Liability Discharge Estimate as of 12/16/96
     (including Copeland Estate Note) = 4,636,025.89

2.   Divide amount in item 1 by $45.25 to get Target
     Liability Discharge Shares:

          $4,636,025.89/$45.25 = 102,453.61
     
3.   Multiply number of shares in item 2 by 110% and round
     to next highest whole number:
     
          102,453.61 x 110% = 112,698.97 rounded to 112,699
     
4.   Subtract current Liability Discharge Shares of 74,518
     from amount in item 3:

     112,699 - 74,518 = 38,181

     This amount will be delivered as additional Liability
     Discharge Shares and Liability Discharge Security
     Shares.
     
5.   The number of shares in item 4 that are Liability
     Discharge Security Shares is determined by subtracting
     10% of the Target Liability Discharge Shares (rounded
     up) by the number of shares previously received as
     Liability Discharge Security Shares (which is 0 on this
     first Determination Date):

     10,245 - 0 = 10,245

6.   The number of shares in item 4 that are Liability
     Discharge Shares is determined by subtracting the
     number of Liability Discharge Security Shares in item 5
     from the total additional shares in item 4:

     38,181 - 10,245 = 27,936

                             A-12


                                                               December 16, 1996
                                                     
                                     SCHEDULE 1.3(c)

                      DISCHARGED LIABILITIES (Revised)
Liability Discharge Amount Per Diem Revised Liability Creditor (as of 12/16/96) Sales Tax Interest Discharge Estimate -------- ------------------- --------- -------- ------------------ 1. First Charter National Bank $1,935,203.63 $22,906.13 $1,958,109.76 a. Loan number: 0537403 ($600,000.00 Line of Credit) b. Loan number: 0527624 ($600,000.00 Line of Credit) c. Loan number: 0527625 ($843,593.77 Note) 2. Associates Commercial Corporation $277,310.50 $1,879.68 $279,190.18 (Clark Credit Corporation) a. Account number: 1929539- 1909056 b. Account number: 1917320- 1917320 c. Account number: 1912014- 1908825 A-13
Liability Discharge Amount Per Diem Revised Liability Creditor (as of 12/16/96) Sales Tax Interest Discharge Estimate -------- ------------------- --------- -------- ------------------ 3. Ford Motor Credit Company $125,155.03 $1,529.69 $126,684.72 (Account number D921) 4. Wachovia Leasing Corporation $1,639,563.52 $62,993.87 $1,702,557.39 (SS#s: 31-34, 36, 38, 40, 42, 43, (1) $23,803.84 (1) $23,803.84 45, 46-54) 5. First Citizens National Bank $107,991.00 $176.12 $108,167.12 and Trust Company 6. Caterpillar Financial Services $21,925.65 $1,315.54 $126.72 $23,367.91 Corporation 7. Copeland Estate Note $409,600.00 $4,545.00 $414,145.00 _____________ __________ __________ _____________ TOTAL REVISED LIABILITY DISCHARGE ESTIMATE (as of 12/16/96) $4,540,553.17 $64,309.41 $31,163.34 $4,636,025.92 ============= ========== ========== ============= A-14
(1) Due 12/5/96