SECOND AMENDMENT TO
                       NOTE AND WARRANT PURCHASE AGREEMENT


         This Second  Amendment  to Note and Warrant  Purchase  Agreement  (this
"Second  Amendment") is dated as of ____________,  1996, and entered into by and
among DATA TRANSMISSION NETWORK CORPORATION, a Delaware corporation ("Company"),
THE  NOTEHOLDERS  LISTED  ON  THE  SIGNATURE  PAGES  HEREOF   (collectively  the
"Noteholders").

                                    RECITALS:

         WHEREAS,  Company and the initial purchaser of the Notes are parties to
that certain Note and Warrant  Purchase  Agreement dated as of June 30, 1994, as
amended by that certain First Amendment to Note and Warrant  Purchase  Agreement
dated as of April 13, 1995 (as amended,  the  "Purchase  Agreement"),  the terms
defined therein being used herein as therein defined; and

         WHEREAS, Company and Noteholders desire to further amend  the Purchase
Agreement as hereinafter set forth;

         NOW,  THEREFORE,  subject to the terms and conditions herein contained,
the parties hereto hereby agree as follows:


         Section 1.  AMENDMENT TO THE PURCHASE AGREEMENT.

         The  definition  of  "Consolidated  Operating  Cash  Flow" set forth in
Section  14  of  the  Purchase   Agreement   hereby  is  amended  by  adding  ",
amortization" immediately after the word "depreciation" in such definition.


         Section 2.  COMPANY'S REPRESENTATIONS AND WARRANTIES.

         In order to induce the Noteholders to enter into this Second  Amendment
and to amend the  Purchase  Agreement  in the manner  provided  herein,  Company
represents  and warrants to the  Noteholders  that the following  statements are
true, correct and complete:

         2.1 Organization and Powers.  Company has all requisite corporate power
and  authority  to  enter  into  this  Second  Amendment  and to  carry  out the
transactions  contemplated  by, and perform its obligations  under, the Purchase
Agreement as amended by this Second Amendment (the "Amended Agreement").

         2.2  Authorization  of  Agreements.  The execution and delivery of this
Second Amendment have been duly authorized by all necessary  corporate action by
Company.


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         2.3 Binding Obligation. This Second Amendment and the Amended Agreement
are the legally valid and binding  obligations  of Company  enforceable  against
Company in accordance with their respective terms,  except as enforcement may be
limited to bankruptcy,  insolvency,  reorganization,  moratorium or similar laws
relating to or limiting  creditors' rights generally or by equitable  principles
relating to enforceability.


         Section 3.  NOTEHOLDERS' REPRESENTATIONS AND WARRANTIES.

         In order to induce  Company to enter into this Second  Amendment and to
amend the Purchase  Agreement in the manner  provided  herein,  the  Noteholders
represent  and warrant to Company  that  collectively  the  Noteholders  are the
holders of more than 50% in  principal  amount of the Notes  outstanding  on the
date of this Second Amendment.


         Section 4.  MISCELLANEOUS.

         4.1 Reference to and Effect on the Purchase  Agreement.  From and after
the date of this Second Amendment,  each reference in the Purchase  Agreement to
"this Agreement",  "hereunder",  "hereof", "herein" or words of like import, and
each reference in any other documents relating to the Purchase Agreement,  shall
mean and be a  reference  to the  Purchase  Agreement  as amended by this Second
Amendment. Except as specifically amended by this Second Amendment, the Purchase
Agreement and other documents relating to the Purchase Agreement shall remain in
full force and effect and are hereby ratified and confirmed.

         4.2 Execution in Counterparts; Effectiveness. This Second Amendment may
be executed in any number of counterparts and by the different parties herein in
separate  counterparts,  each of which when so executed and  delivered  shall be
deemed to be an original and all of which taken  together  shall  constitute but
one and the same  instrument.  This Second Amendment shall become effective upon
the execution of a counterpart hereof by each of the parties hereto.

         4.3  Governing Law.  This Second Amendment shall be governed  by,  and
shall be construed and enforced in accordance with, the laws of the State of New
York.

         4.4 Headings. Section and subsections headings in this Second Amendment
are included herein for convenience of reference only and shall not constitute a
part of this Second  Amendment for any other purpose or be given any substantive
effect.


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         WITNESS the due  execution  hereof by the  respective  duly  authorized
officers of the undersigned as of the date first above written.

                                    COMPANY:

                                    DATA TRANSMISSION NETWORK
                                    CORPORATION, a Delaware corporation



                                    By: _______________________________
                                    Title : ___________________________



                                    NOTEHOLDERS:

                                    EQUITABLE CAPITAL PRIVATE INCOME
                                    AND EQUITY PARTNERSHIP II, L.P.

                                    By:  EQUITABLE CAPITAL MANAGEMENT
                                    CORPORATION, its General Partner



                                    By: _______________________________
                                    Title: Investment Officer

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