MASTER AMENDMENT
                                       TO
                          LOAN AND SECURITY AGREEMENTS


         THIS  MASTER  AMENDMENT  TO  LOAN  AND  SECURITY   AGREEMENTS  ("Master
Amendment") is entered into as of November 30, 1995 among American Communication
Services of Louisville,  Inc., a Delaware corporation  ("Louisville"),  American
Communication  Services  of Fort  Worth,  Inc.,  a Delaware  corporation  ("Fort
Worth"),   American  Communication  Services  of  Columbia,   Inc.,  a  Delaware
corporation ("Columbia"), American Communication Services of Greenville, Inc., a
Delaware corporation  ("Greenville"),  and American Communication Services of El
Paso, Inc. ("E1 Paso"), and collectively  with Louisville,  Fort Worth, Columbia
and Greenville,  the "ACSI Borrower  Subsidiaries")  and AT&T Credit Corporation
("Lender").

                                   WITNESSETH:

         WHEREAS,  each of the ACSI Borrower Subsidiaries is party to a Loan and
Security Agreement with the Lender; specifically described as follows:

         (i)  Louisville  and the Lender are  parties to that  certain  Loan and
Security  Agreement  dated as of October 17,  1994,  as amended by that  certain
Amendment  No. 1 dated as of June 26, 1995 (as the same may from time to time be
further  amended,  modified,  supplemented  or restated,  the  "Louisville  Loan
Agreement");

         (ii) Fort  Worth and the Lender are  parties to that  certain  Loan and
Security  Agreement dated as of February 28, 1995, (as the same may from time to
time be further  amended,  modified,  supplemented or restated,  the "Fort Worth
Loan Agreement");

         (iii)  Columbia,  Greenville and the Lender are parties to that certain
Loan and Security Agreement dated as of June 30, 1995 (as the same may from time
to time be further amended,  modified,  supplemented or restated,  the "Columbia
and Greenville Loan Agreement"); and

         (iv) El Paso  and the  Lender  are  parties  to that  certain  Loan and
Security  Agreement  dated as of September 8, 1995 (as the same may from time to
time be further amended,  modified,  supplemented or restated, the "El Paso Loan
Agreement",  and collectively with the Louisville Loan Agreement, the Fort Worth
Loan  Agreement  and the  Columbia  and  Greenville  Loan  Agreement,  the "Loan
Agreements");

         WHEREAS, Greenville and Columbia have requested the Lender to amend the
Columbia and  Greenville  Loan  Agreement to expand the definition of "Permitted
Liens";


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         WHEREAS,  the Lender has requested that the ACSI Borrower  Subsidiaries
enter into  amendments to the Loan  Agreements on the terms and  conditions  set
forth herein and the ACSI Borrower Subsidiaries have agreed to do so; and

         NOW,  THEREFORE,  in consideration of the premises set forth above, the
terms  and   conditions   contained   herein,   and  other  good  and   valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
ACSI  Borrower  Subsidiaries,  and the  Lender  have  agreed  to amend  the Loan
Agreements as set forth below.  Capitalized  terms used in this Master Amendment
which are not otherwise defined herein, shall have the meanings given such terms
in the  respective  Loan  Agreement  for  each  ACSI  Borrower  Subsidiaries  as
applicable.

         1.  Amendments to Loan Agreements. Effective as of the date hereof and
subject to the satisfaction of the conditions precedent set forth in Section 2
below, on and after the date hereof, the parties hereto agree as follows:

                  1.1 The  definition  of "Cash Flow in Section  1.01 of each of
the Loan  Agreements  except the El Paso Loan  Agreement  is hereby  deleted and
replaced as follows:

                           (a) In the Louisville Loan Agreement and the Fort
Worth Loan Agreement, with the following definition:

                  "Cash Flow" shall mean for any period of the Borrower, (i) Net
Income,  plus (ii) non-cash  charges  deducted in the calculation of Net Income,
plus (iii) Headquarters  Expenses,  plus (iv) actual payments of interest on the
Loans and actual amounts paid with respect to other Debt for such period.

                           (b) In the Columbia and Greenville Loan Agreement,
with the following definition:

                  "Cash Flow"  shall mean for any period of any Person,  (i) Net
Income,  plus (ii) non-cash  charges  deducted in the calculation of Net Income,
plus (iii) Headquarters  Expenses,  plus (iv) actual payments of interest on the
Loans and actual amounts paid with respect to other Debt for such period.

                  1.2 The definition of "Fixed  Charges" in Section 1.01 of each
of the Loan  Agreements  except the El Paso Loan Agreement is hereby deleted and
replaced with the following:

                           (a) In the Louisville Loan Agreement, the Fort Worth
Loan Agreement, and the El Paso Loan Agreement with the following definition:

                           "Fixed Charges" shall mean, with respect to any
fiscal period of Borrower, the sum of the following amounts

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calculated  at the end of such  period:  (i)  scheduled  payments of  principal,
interest,  rent and other amounts payable with respect to Debt (other than those
required to be made with  respect to the Loans)  during such  period,  plus (ii)
fees payable by the Borrower to the Lender (excluding fees and expenses accrued,
incurred  or paid on or  prior  to the  Effective  Date)  plus  (iii)  scheduled
quarterly principal and interest payments required to be made during such period
with  respect to the Loans and solely  with  respect  to  calculating  the Fixed
Charge  Coverage  Ratio in clause  (v) of Section  6.04,  the  accrued  Deferral
Amounts and accrued Deferrable Interest Arrearages.

                           (b) In the Columbia and Greenville Loan Agreement,
with the following definition:

                           "Fixed Charges" shall mean, with respect to any
fiscal period of either Borrower, the sum of the following amounts calculated at
the end of such period: (i) scheduled payments of principal,  interest, rent and
other amounts payable with respect to Debt (other than those required to be made
with  respect to the Loans)  during such  period,  plus (ii) fees payable by the
Borrower to the Lender (excluding fees and expenses accrued, incurred or paid on
or prior to the Effective  Date) plus (iii)  scheduled  quarterly  principal and
interest  payments  required to be made  during such period with  respect to the
Loans and solely with respect to calculating  the Fixed Charge Coverage Ratio in
clause (v) of Section 6.04, the accrued Deferral Amounts and accrued  Deferrable
Interest Arrearages.

                  1.3 Section 1.01 of each of the Loan Agreements  except the El
Paso Loan  Agreement is amended by deleting the  definition  of "Fixed Rate" and
Variable  Rate" in their  entirety and replacing  with the following  respective
definitions:

                           "Fixed Rate" shall mean, with respect to (i) each
Loan which originally bore interest at a fixed rate, a rate equal to the average
of the "ask yields" of United States  Treasury Notes trading  closest to par and
maturing in the month seven years from the month of the making of such Loan,  as
quoted in the  Eastern  Edition of The Wall  Street  Journal  (or any  successor
publication)  on a date two (2) Business Days prior to the date of the making of
such Loan (or if there is no United States Treasury Note maturing in such month,
an  interpolation  by Lender  (evidence of which is provided to the Borrower) of
the "ask yields" of United  States  Treasury  Notes  trading  closest to par and
maturing  in the  month  closest  but prior to,  and in the  month  closest  but
subsequent  to, the month seven years from the month of the making of such Loan,
as quoted in the Eastern  Edition of The Wall Street  Journal (or any  successor
publication)  on the date two (2) Business  Days prior to the date of the making
of such Loan), plus in either case, the Applicable Margin and (ii) each Variable
Rate Loan  converted to a Fixed Rate Loan pursuant to the  provisions of Section
2.05, a rate

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<PAGE>



equal to the average of the "ask yields" of United States Treasury Notes trading
closest to par and maturing in the month seven years from the month in which the
Conversion  Date  occurs,  as quoted in the  Eastern  Edition of The Wall Street
Journal (or any successor  publication)  on the date two (2) Business Days prior
to the Conversion  Date (or if there is no United States  Treasury Note maturing
in such month, an interpolation of the "ask yields" by Lender (evidence of which
is provided to the Borrower) of United  States  Treasury  Notes  maturing in the
month  closest but prior to, and in the month closest but  subsequent  to, seven
years  after the month in which the  Conversion  Date  occurs,  as quoted in the
Eastern Edition of The Wall Street Journal (or any successor publication) on the
date two (2) Business Days prior to the Conversion  Date),  plus in either case,
the Applicable Margin.

                  "Variable  Rate"  shall  mean with  respect to each Loan which
bears interest at a variable rate, the average offering rate by commercial paper
dealers for three month commercial paper of major  corporations as quoted in the
Eastern Edition of The Wall Street Journal (or its successor publication) (i) in
effect two (2)  Business  Days prior to the date of the making of such Loan with
respect to the period  commencing on such date and ending on the last day of the
calendar quarter in which such date occurs,  and (ii) in effect two (2) Business
Days prior to the first day of each subsequent  calendar quarter with respect to
the  period  commencing  on such  first  day and  ending on the last day of such
subsequent calendar quarter, plus, in each case, the Applicable Margin.

                  1.4 Section 1.01 of each of the Loan Agreements  except the El
Paso Loan  Agreement is hereby  amended to delete the  definitions of the "Fixed
Rate Note" and the "Variable Rate Note".

                  1.5 Section 1.01 is hereby amended in all of the Loan
Agreements to add the following definition (to be inserted
alphabetically):

                           "Default" shall mean an event which with the giving
of notice or passage of time or both would constitute an Event of
Default.

                  1.6 Section 6.01 of the Columbia and Greenville Loan Agreement
is amended to delete the word "and" at the end of clause  (iv)  thereof,  to add
the word "and" at the end of clause (v) thereof and to add the following  clause
(vi) thereto:

                           (vi) the rights of MPX Systems, Inc., a South
Carolina corporation ("MPX"), pursuant to that certain License Agreement entered
into on July 26, 1995 between MPX and columbia.

         2. Conditions of Effectiveness of this Master Amendment.  This Master
Amendment shall become effective and be deemed

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<PAGE>



effective on the date first above  written  subject to the  Lender's  receipt of
each of the following:

                           (i)  five (5) originals of this Master Amendment,
duly executed by the ACSI Borrower Subsidiaries and the Lender; and

                           (ii) five (5) originals of the Master Reaffirmation
of Parent Pledge and Support Agreements attached as Exhibit A
hereto.

         3. Further Assurances. The ACSI Borrower Subsidiaries hereby agree from
time to time,  as and when  requested  by the Lender,  to execute and deliver or
cause  to be  executed  and  delivered,  all  such  documents,  instruments  and
agreements  and to take or cause to be taken such further or other action as the
Lender  may deem  necessary  or  desirable  in order to carry out the intent and
purposes  of this  Master  Amendment,  the Loan  Agreements  or the  other  Loan
Documents.

         4. Representations  and Warranties of the ACSI Borrower  Subsidiaries.
The ACSI  Borrower  Subsidiaries  hereby  represent and warrant that this Master
Amendment and their  respective  Loan  Agreement as  previously  executed and as
amended  hereby,   constitute  legal,  valid  and  binding  obligations  of  the
respective ACSI Borrower  Subsidiary and are enforceable  against the respective
ACSI Borrower Subsidiary in accordance with their terms.

         5. Reference to the Effect on the Agreement.

                  (a) Upon the  effectiveness of Section 1 hereof,  on and after
the date  hereof,  each  reference in the Loan  Agreement  to "this  agreement,"
"hereunder,"  "hereof,"  "herein"  or words of like  import  shall mean and be a
reference to the respective Loan Agreement as amended hereby.

                  (b) Except as specifically  set forth above,  each of the Loan
Agreements, and all other documents,  instruments and agreements executed and/or
delivered in connection  therewith,  shall remain in full force and effect,  and
are hereby ratified and confirmed.

                  (c) The execution,  delivery and  effectiveness of this Master
Amendment shall not, except as expressly provided herein, operate as a waiver of
any  right,  power or  remedy  of the  Lender,  nor  constitute  a waiver of any
provision  of the Loan  Agreements,  or any  other  documents,  instruments  and
agreements executed and/or delivered in connection therewith.

         6. Headings. Section headings in this Master Amendment are included
herein for convenience of reference only and shall not constitute a part of this
Master Amendment for any other purpose.


                                       -5-

<PAGE>



         7. Counterparts;  Facsimile  Signatures.  This Master Amendment may be
executed by one or more of the parties to the Master  Amendment on any number of
separate  counterparts  and all of said  counterparts  taken  together  shall be
deemed to constitute  one and the same  instrument.  Each of the parties  hereto
agrees that a signature transmitted by facsimile transmission shall be effective
to bind the party so transmitting its signature.

         8. Entire  Agreement.  This Master  Amendment,  taken together with the
respective  Loan  Agreements  and all of the other  respective  Loan  Documents,
embodies  the entire  agreement  and  understanding  of the  parties  hereto and
supersedes all prior agreements and  understandings,  written and oral, relating
to the subject matter hereof.

         9. Applicable  Law;  Severability.  This  Master  Amendment  shall  be
governed by, and construed in accordance  with, the internal laws (as opposed to
the  conflict  of laws  provisions)  and  decisions  of the State of New Jersey.
Whenever possible,  each provision of this Master Amendment shall be interpreted
in such manner as to be effective  and valid under  applicable  law, but, if any
provision of this Master  Amendment  shall be held to be  prohibited  or invalid
under  applicable law, such provision shall be ineffective only to the extent of
such  prohibition  or  invalidity,  without  invalidating  the remainder of such
provision or the remaining provisions of this Master Amendment.

         IN WITNESS WHEREOF,  this Master Amendment has been duly executed as of
the date set forth above.

                                       AMERICAN COMMUNICATION SERVICES
                                         OF LOUISVILLE, INC.

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

                                       AMERICAN COMMUNICATION SERVICES
                                         OF FORT WORTH, INC.

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

                                       -6-

<PAGE>



                                        AMERICAN COMMUNICATION SERVICES
                                          OF COLUMBIA, 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 LOUISVILLE, 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

                                        AT&T CREDIT CORPORATION

                                        By:----------------------------
                                        Name:  Edward F. Gromek
                                        Title:  Vice President


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<PAGE>



     IN WITNESS WHEREOF,  this Master Amendment has been duly executed as of the
date set forth above.

                                        AMERICAN COMMUNICATION SERVICES
                                           OF LOUISVILLE, INC.

                                        By:----------------------------
                                        Name:-------------------------- 
                                        Title:-------------------------

                                        AMERICAN COMMUNICATION SERVICES
                                           OF FORT WORTH, INC.

                                        By:----------------------------
                                        Name:--------------------------
                                        Title:-------------------------

                                        AMERICAN COMMUNICATION SERVICES
                                           OF COLUMBIA, INC.

                                        By:----------------------------
                                        Name:--------------------------
                                        Title:-------------------------

                                        AMERICAN COMMUNICATION SERVICES
                                          OF GREENVILLE, INC.

                                        By:----------------------------
                                        Name:--------------------------
                                        Title:-------------------------


                                        AMERICAN COMMUNICATION SERVICES
                                          OF EL PASO, INC.

                                        By:----------------------------
                                        Name:--------------------------
                                        Title:-------------------------

                                        AT&T CREDIT CORPORATION

                                        /s/ EDWARD F. GROMEK
                                        Name: Edward F. Gromek
                                        Title: Vice President

                                       -8-

<PAGE>



                                                               EXHIBIT A

                             MASTER REAFFIRMATION OF
                      PARENT PLEDGE AND SUPPORT AGREEMENTS

         This MASTER REAFFIRMATION OF PARENT PLEDGE AND SUPPORT AGREEMENTS (this
"Reaffirmation")  is executed as of this 30th day of November,  1995 by American
Communications  Services,  Inc., a Delaware corporation (the "Parent"), in favor
of AT&T Credit Corporation, a Delaware corporation ("Lender").

                                   WITNESSETH:

         WHEREAS, American Communications Services of Louisville, Inc.,
American Communication Services of Fort Worth, Inc. and American Communication
Services of Columbia, Inc., American Communication Services of Greenville, Inc.,
and American Communication Services of El Paso, Inc. (each a Delaware
corporation), entered into those certain Loan and Security Agreements each dated
respectively as of October 16, 1994, February 28, 1995, June 30, 1995 and
September 9, 1995 (collectively, as so amended and as further amended, restated
or modified. the "Loan Agreements") with Lender;

         WHEREAS,  to induce  Lender to enter  into the Loan  Agreement,  Parent
executed and delivered  those certain Parent Pledge and Support  Agreements each
dated as of October 16, 1994,  February 28, 1995, June 30, 1995 and September 9,
1995 (collectively,  as so amended and as further amended, restated or modified,
the "Pledge Agreements") in favor of the Lender;

         WHEREAS,  the parties to the Loan  Agreements  are  entering  into that
certain Master Amendment (the "Amendment") of even date herewith; and

         WHEREAS,  it is a  condition  precedent  to  the  effectiveness  of the
Amendment that Parent execute and deliver this Reaffirmation:

         NOW, THEREFORE, for and in consideration of the foregoing and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Parent hereby agrees as follows:

         1. Reaffirmation of Pledge Agreement. The Parent acknowledges that it
has reviewed the Amendment and reaffirms that the Pledge Agreements shall
continue in full force and effect in accordance with their respective terms
notwithstanding the execution and delivery of the Amendment.

         2.  Governing Law and Jurisdiction. This Reaffirmation shall be
construed in accordance with and governed by the internal laws of the State of
New Jersey, without giving effect to any conflicts of laws principles.

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<PAGE>




         3.  Execution in Counterparts. This Reaffirmation may be executed in
any number of counterparts, each of which shall be an original, but all of which
shall together constitute one and the same agreement.

         IN WITNESS WHEREOF,  the parties hereto have caused this  Reaffirmation
to be duly executed by their duly authorized  representatives  as of the day and
year first written above.

                                                 AMERICAN COMMUNICATIONS
                                                        SERVICES, INC.

                                                 By:----------------------------
                                                 Name:--------------------------
                                                 Title:-------------------------


Acknowledged and agreed to
as of the day and year first
written above.

AT&T CREDIT CORPORATION

By:----------------------------
Name:--------------------------
Title:-------------------------

                                       -2-