December 19, 1995


AT&T Credit Corporation
44 Whippany Road
Morristown, New Jersey  07962

Gentlemen:

                  AT&T Credit Corporation ("AT&T") is currently a party to Loan
and Security Agreements ("AT&T Loan Agreements") with various subsidiaries (the
"Funded Subsidiaries") of American Communications Services, Inc.  The Funded
Subsidiaries which are the subject of this letter include American Communication
Services of Fort Worth, Inc. ("Fort Worth"), American Communication Services of
Greenville, Inc. ("Greenville"), American Communication Services of Columbia,
Inc. ("Columbia") and American Communication Services of El Paso, Inc. ("El
Paso").

                  Each  AT&T  Loan   Agreement   provides  for  a  Capital  Loan
Commitment   Amount  and  an  Equipment  Loan  Commitment   Amount.  It  is  the
understanding of the Funded  Subsidiaries  that AT&T is agreeable to an increase
in  the  Capital  Loan  Equipment  Amount  for  each  Funded  Subsidiary  with a
corresponding  decrease in the Equipment Loan  Equipment  Amount for each Funded
Subsidiary.  The Funded  Subsidiaries  and AT&T therefore  hereby agree that the
Capital Loan Equipment Amount for each Funded  Subsidiary shall equal 90% of the
respective  aggregate  Commitment  Amount and that the Equipment Loan Commitment
Amount for each Funded  Subsidiary  shall equal 10% of the respective  aggregate
Commitment Amount.  Based upon an aggregate Commitment Amount for (i) Fort Worth
of $5,500,000,  (ii) Greenville of $5,200,000,  (iii) Columbia of $5,000,000 and
(iv) El Paso of $5,500,000,  the Funded  Subsidiaries and AT&T hereby agree that
the  definitions  shall be amended in each of the respective  Loan Agreements to
read as follows:


         1.  Fort Worth:  "Capital Loan Commitment Amount" shall mean the
lesser of (i) $4,950,000, inclusive of capitalized interest, if any, on the
Capital Loans and (ii) ninety percent (90%) of the outstanding principal balance
of all then outstanding Loans, inclusive of capitalized interest."

                  "Equipment Loan Commitment Amount" shall mean $550,000,
inclusive of capitalized interest, if any, on the Equipment Loans."




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AT&T Credit Corporation
December 19, 1995

         2.  Greenville:  "ACS Greenville Capital Loan Commitment Amount" shall
mean the lesser of (i) $4,680,000, inclusive of capitalized interest, if any, on
the ACS Greenville Capital Loans and (ii) ninety percent (90%) of the
outstanding principal balance of all Loans made by Lender to ACS Greenville,
inclusive of capitalized interest."

                  "ACS Greenville  Equipment Loan Commitment  Amount" shall mean
$520,000,  inclusive  of  capitalized  interest,  if any, on the ACS  Greenville
Equipment Loans."


         3.  Columbia:  "ACS Columbia Capital Loan Commitment Amount" shall
mean the lesser of (i) $4,500,000, inclusive of capitalized interest, if any, on
the ACS Columbia Capital Loans and (ii) ninety percent (90%) of the outstanding
principal balance of all Loans made by Lender to ACS Columbia, inclusive of
capitalized interest."

                  "ACS Columbia  Equipment  Loan  Commitment  Amount" shall mean
$500,000,  inclusive  of  capitalized  interest,  if any,  on the  ACS  Columbia
Equipment Loans."


         4.  El Paso:  "Capital Loan Commitment Amount" shall mean the lesser of
(i) $4,950,000, inclusive of capitalized interest, if any, on the Capital Loans
and (ii) ninety percent (90%) of the outstanding principal balance of all then
outstanding Loans, inclusive of captialized interest."

                  "Equipment Loan Commitment Amount" shall mean $550,000,
inclusive of capitalized interest, if any, on the Equipment Loans."


                  Each of the  Funded  Subsidiaries  and AT&T also agree that to
the  extent  (i) an amount  previously  borrowed  by a Funded  Subsidiary  as an
Equipment  Loan  exceeds the stated  amount for the  respective  Equipment  Loan
Commitment  Amount  or  (ii)  an  amount  borrowed  in the  future  by a  Funded
Subsidiary  as a Capital Loan exceeds the Capital Loan  Commitment  Amount,  but
does not in either case cause the aggregate of the then  outstanding  respective
Capital  Loans and  Equipment  Loans for that  Funded  Subsidiary  to exceed the
aggregate  Commitment  Amount set forth above, such excess shall be treated as a
Capital Loan.



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AT&T Credit Corporation
December 19, 1995


                  Greenville,  Columbia  and  AT&T  therefore  also  agree  that
Section  2.08(f) of the respective  Loan  Agreement  shall be amended so that it
shall read in its entirety as follows:

                  "If the aggregate  principal balance (inclusive of capitalized
interest) of (i) either  Borrower's  Equipment  Loans  exceeds  such  Borrower's
Equipment Loan Commitment Amount or (ii) either Borrower's Capital Loans exceeds
such  Borrower's  Capital Loan  Commitment  Amount,  but in either case does not
cause  the  aggregate  of the then  outstanding  respective  Capital  Loans  and
Equipment Loans for such Borrower to exceed the amount which is the aggregate of
such  Borrower's  Equipment Loan  Commitment  Amount and Capital Loan Commitment
Amount, such excess shall be treated as a Capital Loan. Otherwise,  then in each
such case,  such Borrower shall  immediately  repay to Lender,  upon notice from
Lender, the amount by which the outstanding  principal balance of the respective
Loan Balance exceeds its respective Commitment Amount, together with all accrued
and unpaid interest on such excess principal up to the date of repayment."


                  Fort Worth, El Paso and AT&T therefore also agree that Section
2.08(f) of the respective Loan Agreements shall be amended so that it shall read
in its entirety as follows:

                  "If the aggregate  principal balance (inclusive of capitalized
interest) of (i) the  Equipment  Loans  exceeds the  Equipment  Loan  Commitment
Amount or (ii) the Capital Loans exceeds the Capital Loan Commitment Amount, but
in either  case does not cause the  aggregate  of the then  outstanding  Capital
Loans and  Equipment  Loans to exceed the amount  which is the  aggregate of the
Equipment Loan Commitment Amount and Capital Loan Commitment Amount, such excess
shall be treated as a Capital Loan. Otherwise,  then in each such case, Borrower
shall immediately repay to Lender,  upon notice from Lender, the amount by which
the  outstanding  principal  balance of the respective  Loan Balance exceeds its
respective  Commitment Amount,  together with all accrued and unpaid interest on
such excess principal up to the date of repayment."


                  Each  Funded   Subsidiary   and  AT&T  also  agrees  that  the
respective  amended  definitions  as set forth above shall be given  retroactive
effect,  such that the operation of the amended  definitions shall not (i) cause
such Funded Subsidiary to be in violation of Section 4.02(b), Section 4.02(d) or
Section 6.02 of the respective  Loan Agreement or (ii) cause an Event of Default
under Section 8.01(b) under the respective Loan Agreement.

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                  Please   sign  where   indicated   below  to   indicate   your
acknowledgment and agreement with the foregoing.


                                             AMERICAN COMMUNICATION SERVICES
                                                   OF FORT WORTH, INC.

                                             /s/ RICHARD A. KOZAK
                                             Name: Richard A. Kozak
                                             Title: President & Chief
                                                    Executive Officer


                                              AMERICAN COMMUNICATION SERVICES
                                                   OF GREENVILLE, INC.

                                              /s/ RICHARD A. KOZAK
                                              Name: Richard A. Kozak
                                              Title: President & Chief
                                                     Executive Officer

                         
                                             AMERICAN COMMUNICATION SERVICES
                                                    OF COLUMBIA, INC.
                                             /s/ RICHARD A. KOZAK
                                             Name: Richard A. Kozak
                                             Title: President & Chief
                                                     Executive Officer


                                            AMERICAN COMMUNICATION SERVICES
                                               OF EL PASO, INC.
               
                                            /s/ RICHARD A. KOZAK
                                            Name: Richard A. Kozak
                                            Title: President & Chief
                                                    Executive Officer



ACKNOWLEDGED AND AGREED
-----------------------

AT&T CREDIT CORPORATION

By:  __________________________

Name:  ________________________

Title:  _______________________

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