AMENDMENT, dated as of April 10,
                                       2000  (the  "Agreement"),   between   ICG
                                       Communications,    Inc.,   a     Delaware
                                       corporation  (the  "Company"),   and  the
                                       Purchasers  whose signatures appear below
                                       (the "Purchasers").

                  WHEREAS,  reference is made to the Preferred Stock and Warrant
Purchase Agreement dated as of February 27, 2000 (the "Purchase Agreement"),  by
and between the Company and the  Purchasers.  Capitalized  terms used herein but
not  otherwise  defined  shall  be given  the  meaning  ascribed  to them in the
Purchase Agreement;

                  WHEREAS,  pursuant to an Assignment of Rights Under  Preferred
Stock  and  Warrant  Purchase  Agreement  dated  as of March  8,  2000,  HM4 ICG
Qualified  Fund, LLC, HM4 ICG Private Fund, LLC, HM PG-IV ICG, LLC, HM 4-SBS ICG
Coinvestors,  LLC, and HM 4-EQ ICG  Coinvestors  became  parties to the Purchase
Agreement;

                  WHEREAS,  in  accordance  with  Section  8.6 of  the  Purchase
Agreement,  the parties  hereto  desire to amend the Purchase  Agreement as more
fully set forth below in order to reflect (1) the  redesignation of the Series A
Preferred Stock into Series A-1 Preferred  Stock (as defined below),  Series A-2
Preferred  Stock (as defined  below) and Series A-3 Preferred  Stock (as defined
below),  (2) the  increase of the initial  Liquidation  Preference  per share of
Series A Preferred  Stock from  $1,000 to $10,000 per share and the  concomitant
reduction  in the number of shares of Series A Preferred  Stock being  issued by
the Company and purchased by the Purchasers and (3) related conforming changes;

                  NOW, THEREFORE, in consideration of the foregoing,  and of the
covenants and agreements contained herein, the parties hereby agree as follows:

         1.   Amendment of Recitals. The  recitals  of  the  Purchase  Agreement
shall be  amended  by deleting  the first "Whereas" clause  in its entirety  and
substituting, in lieu thereof, the following:

                  "WHEREAS,  the  Company  proposes,  subject  to the  terms and
                  conditions  set  forth  herein,  to  issue  and  sell  to  the
                  Purchasers  50,000  shares  of its 8% Series  A-1  Convertible
                  Preferred  Stock  due  2015,  initial  liquidation  preference
                  $10,000 per share,  par value $0.01 per share (the "Series A-1
                  Preferred  Stock"),   23,000  shares  of  its  8%  Series  A-2
                  Convertible  Preferred  Stock  due 2015,  initial  liquidation
                  preference  $10,000 per share,  par value $0.01 per share (the
                  "Series  A-2  Preferred  Stock")  and  2,000  shares of its 8%
                  Series  A-3  Convertible  Preferred  Stock due  2015,  initial
                  liquidation  preference $10,000 per share, par value $0.01 per
                  share (the "Series A-3 Preferred  Stock" and together with the
                  Series A-1 Preferred Stock and the Series A-2 Preferred Stock,
                  the "Series A Preferred Stock");"

<PAGE>


         2.   Amendment of Definitions.  Section  (a)  of Article  I  is  hereby
amended by inserting or amending, as the case may be, the following definitions:

                  ""Amending  Agreement"  means the Amendment  dated as of April
10, 2000 by and among the Company and the other parties  listed on the signature
pages thereof."

                  ""Equity  Documents"  means this Agreement,  the  Registration
Rights  Agreement,  the  Certificate  of  Designation,   the  Management  Rights
Agreements,  the  Share  Exchange  Agreement,  the  Warrants  and  the  Amending
Agreement."

                  ""HMTF Issued Series A Preferred Shares" shall mean the shares
of Series A-2 Preferred Stock issued to members of the HMTF Group on the Closing
Date under this Agreement."

                  ""Liberty  Issued  Series A Preferred  Shares"  shall mean the
shares of Series A-1  Preferred  Stock issued to members of the Liberty Group on
the Closing Date under this Agreement."

                  ""Registration Rights Agreement" means the Registration Rights
Agreement  dated  as of  April  7,  2000,  by and  among  the  Company  and  the
Purchasers, in the form attached hereto as Exhibit C."

                  ""Series A-1 Preferred Stock" has the meaning set forth in the
first recital to this Agreement."

                  ""Series A-2 Preferred Stock" has the meaning set forth in the
first recital to this Agreement."

                  ""Series A-3 Preferred Stock" has the meaning set forth in the
first recital to this Agreement."

         3.   Amendment of Section 2.1. The Purchase Agreement is hereby amended
by  deleting "one  thousand dollars ($1,000) per  share" in  the  fifth  line of
Section 2.1 and substituting, in lieu  thereof, "ten thousand  dollars ($10,000)
per share."

         4.   Amendment of Section 5.2.

               (a) The Purchase Agreement is hereby amended by deleting  Section
5.2(a) in its entirety and substituting, in lieu thereof, the following:

                  " For  so  long  as  the  members  of the  HMTF  Group  in the
                  aggregate  own any  combination  of shares of Common Stock and
                  Series A-2 Preferred  Stock  representing  an amount of Common
                  Stock (on an as-converted basis) that, taken together,  equals
                  at least 4,107,143 shares of Common Stock (as adjusted for any
                  stock  dividends,  splits and  combinations and similar events
                  affecting the Common Stock from time to time),  the holders of
                  a majority of the then  outstanding HMTF Shares shall have the
                  right to designate  one person for  election to the  Company's



                                       2
<PAGE>

                  Board of  Directors  or, if  greater,  such  number of persons
                  (rounded up to the next whole number) equal to 10% of the then
                  authorized  number  of  members  of  the  Company's  Board  of
                  Directors  (each such  person an "HMTF  Director");  provided,
                  however,  that the right to designate an HMTF  Director  under
                  this  Section  5.2  shall be  suspended  at any time  that the
                  holders of the Series  A-2  Preferred  Stock have the right to
                  elect a person  to the Board of  Directors  under the terms of
                  the Series A-2 Preferred Stock set forth in the Certificate of
                  Designation.  In the event the  holders of a  majority  of the
                  then  outstanding  HMTF Shares are entitled under this Section
                  5.2  to  designate  an  HMTF  Director  for  election  to  the
                  Company's   Board  of  Directors  and  so  designate  an  HMTF
                  Director,  they shall so notify the Company in writing and the
                  Company  shall use its best  efforts  (a) to cause the size of
                  the Board of  Directors to be increased by one and the vacancy
                  created  thereby to be filled by electing an HMTF Director and
                  (b) in  connection  with the  meeting of  stockholders  of the
                  Company  next  following  such  election,  to  cause  an  HMTF
                  Director  to be  nominated  for  election as a director by the
                  stockholders  and to cause the HMTF Director to be so elected.
                  If the  holders of a  majority  of the then  outstanding  HMTF
                  Shares are  entitled  under this  Section 5.2 to  designate an
                  HMTF Director for election to the Company's Board of Directors
                  and a vacancy  shall exist in the office of an HMTF  Director,
                  the holders of a majority of the then  outstanding HMTF Shares
                  shall be  entitled to  designate a successor  and the Board of
                  Directors  shall  use  its  best  efforts  to (x)  elect  such
                  successor   and  (y)  in   connection   with  the  meeting  of
                  stockholders  of the Company  next  following  such  election,
                  cause such  successor to be nominated for election as director
                  by the stockholders and to be elected."

               (b) The Purchase Agreement is hereby amended by deleting  Section
5.2(b)(i) in its entirety and substituting, in lieu thereof, the following:

                  " For so long  as the  members  of the  Liberty  Group  in the
                  aggregate  own any  combination  of shares of Common Stock and
                  Series A-1 Preferred  Stock  representing  an amount of Common
                  Stock (on an as-converted basis) that, taken together,  equals
                  at least 2,687,571 shares of Common Stock (as adjusted for any
                  stock  dividends,  splits and  combinations and similar events
                  affecting the Common Stock from time to time),  the members of
                  the Liberty  Group,  voting  together  as a single  class by a
                  plurality  of the votes  cast or by the  written  consent of a
                  majority in interest  of such  members,  shall have a right to
                  designate  one person for election to the  Company's  Board of
                  Directors or, if greater,  such number of persons  (rounded up
                  to the next whole number) equal to 10% of the then  authorized
                  number of members of the  Company's  Board of Directors  (each


                                       3
<PAGE>


                  such person a "Liberty Director"); provided, however, that the
                  right to designate a Liberty  Director  under this Section 5.2
                  shall be  suspended at any time that the holders of the Series
                  A-1  Preferred  Stock  have the right to elect a person to the
                  Board of Directors under the terms of the Series A-1 Preferred
                  Stock  set forth in the  Certificate  of  Designation.  In the
                  event the members of the Liberty Group are entitled under this
                  Section 5.2 to designate the Liberty  Director for election to
                  the  Company's  Board of Directors and elect to so designate a
                  Liberty Director,  they shall so notify the Company in writing
                  and the  Company  shall use its best  efforts (a) to cause the
                  size of the Board of  Directors to be increased by one and the
                  vacancy  created  thereby  to be filled by  electing a Liberty
                  Director   and  (b)  in   connection   with  the   meeting  of
                  stockholders  of the Company next following such election,  to
                  cause a Liberty  Director  to be  nominated  for  election  as
                  director by the stockholders and to cause the Liberty Director
                  to be so  elected.  If the  members of the  Liberty  Group are
                  entitled  under  this  Section  5.2  to  designate  a  Liberty
                  Director for election to the Company's  Board of Directors and
                  a vacancy shall exist in the office of a Liberty Director, the
                  members of the  Liberty  Group,  voting  together  as a single
                  class  by a  plurality  of the  votes  cast or by the  written
                  consent of a majority in interest  of such  members,  shall be
                  entitled to  designate a successor  and the Board of Directors
                  shall use its best efforts to (x) elect such successor and (y)
                  in connection  with the meeting of stockholders of the Company
                  next  following  such  election,  cause such  successor  to be
                  nominated for election as director by the  stockholders and to
                  be elected."

               (c) The Purchase  Agreement is hereby amended by deleting Section
5.2(b)(ii) in its entirety and substituting, in lieu thereof, the following:

                  " For so long as the  members  of the  Liberty  Group  own any
                  combination of shares of Common Stock and Series A-1 Preferred
                  Shares   representing   an  amount  of  Common  Stock  (on  an
                  as-converted  basis) that,  taken together,  equals  8,928,571
                  shares of Common Stock (as  adjusted for any stock  dividends,
                  splits and  combinations  and  similar  events  affecting  the
                  Common  Stock from time to time),  the  members of the Liberty
                  Group, voting together as a single class by a plurality of the
                  votes cast or by the written consent of a majority in interest
                  of such members, shall have a right, in addition to the rights
                  set forth in clause (i) above,  to  designate  one  additional
                  person for election to the Company's Board of Directors or, if
                  greater,  such number of additional persons (rounded up to the
                  next whole number) equal to 10% of the then authorized  number
                  of  members of the  Company's  Board of  Directors  (each such
                  person an "Additional Liberty Director");  provided,  however,



                                       4
<PAGE>

                  that the right to designate  an  Additional  Liberty  Director
                  under this Section 5.2 shall be suspended at any time that the
                  holders of the Series  A-1  Preferred  Stock have the right to
                  elect a person  to the Board of  Directors  under the terms of
                  the Series A-1 Preferred Stock set forth in the Certificate of
                  Designation. In the event the members of the Liberty Group are
                  entitled  under this Section 5.2 to  designate  an  Additional
                  Liberty  Director  for  election  to the  Company's  Board  of
                  Directors  and elect to so  designate  an  Additional  Liberty
                  Director,  they shall so notify the Company in writing and the
                  Company  shall use its best  efforts  (a) to cause the size of
                  the Board of  Directors to be increased by one and the vacancy
                  created thereby to be filled by electing an Additional Liberty
                  Director   and  (b)  in   connection   with  the   meeting  of
                  stockholders  of the Company next following such election,  to
                  cause an  Additional  Liberty  Director  to be  nominated  for
                  election  as  director  by the  stockholders  and to  cause an
                  Additional  Liberty Director to be so elected.  If the members
                  of the Liberty  Group are  entitled  under this Section 5.2 to
                  designate an Additional  Liberty  Director for election to the
                  Company's  Board of Directors and a vacancy shall exist in the
                  office of an Additional  Liberty Director,  the members of the
                  Liberty  Group,  voting  together  as  a  single  class  by  a
                  plurality  of the votes  cast or by the  written  consent of a
                  majority  in interest  of such  members,  shall be entitled to
                  designate a successor and the Board of Directors shall use its
                  best efforts to (x) elect such successor and (y) in connection
                  with the meeting of stockholders of the Company next following
                  such  election,  cause  such  successor  to be  nominated  for
                  election as director by the stockholders and to be elected."

         5.   Amendment of Section 5.16.  Section 5.16 of the Purchase Agreement
is  hereby   amended  by  deleting   the  third  sentence  in  it  entirety  and
substituting, in lieu thereof, the following sentence:

                  " This  proportional  purchase right shall not apply to shares
                  issued pursuant to the Share Exchange Agreement, any rights or
                  obligations  referenced on Schedule 3.2, any shares of capital
                  stock  issued by the  Company  in lieu of any fees  payable in
                  connection  with the  Transaction  to the Company's  financial
                  advisors,  any shares issued pursuant to any stock option plan
                  or  arrangement  or  employee   benefit  plan  or  arrangement
                  existing  as of the date hereof or  hereafter  approved by the
                  Board of  Directors  of the  Company  or the  shares of Common
                  Stock issued from time to time upon conversion of the Series A
                  Preferred Stock or upon exercise of the Warrants."

         6.   Amendment of Schedule I.  Schedule I to  the Purchase Agreement is
hereby amended by deleting it in its entirety and substituting, in lieu thereof,
Schedule I attached hereto.


                                       5
<PAGE>



         7.   No Other Waivers.  Except as expressly provided in this Agreement,
each of the terms and provisions of the Purchase  Agreement shall remain in full
force and effect in accordance with its terms.

         8.   Counterparts.  This  Agreement  may  be  executed  in  one or more
counterparts, each of which shall be deemed to be an original,  but all of which
taken together shall constitute one and the same instrument.

         9.   Governing Law.  This Agreement shall be governed by, and construed
in accordance with, the laws of the State of New York (without giving  effect to
principles of conflicts of law).

         10.  Headings.  The  headings  used  herein  are   for  convenience  of
reference only and shall not affect the construction of, nor shall they be taken
in consideration in interpreting, this Agreement.


                                       6
<PAGE>




                  IN WITNESS WHEREOF, the  undersigned  have  duly executed  and
delivered this Amendment as of the date first written above.


                                             ICG COMMUNICATIONS, INC.

                                             By: /s/ H. Don Teague
                                                --------------------------------
                                                Name: H. Don Teague
                                                Title:  Executive Vice President


<PAGE>






                                             HMTF BRIDGE ICG, LLC
                                             HM4 ICG QUALIFIED FUND, LLC
                                             HM4 ICG PRIVATE FUND, LLC
                                             HM PG-IV ICG, LLC
                                             HM 4-SBS ICG COINVESTORS, LLC
                                             HM 4-EQ ICG COINVESTORS, LLC

                                             By: /s/ David W. Knickel
                                                --------------------------------
                                                Name: David W. Knickel
                                                Title: President


<PAGE>

                                             Liberty Media Corporation

                                             By: /s/ Charles Y. Tanabe
                                                --------------------------------
                                                Name: Charles Y. Tanabe
                                                Title: Senior Vice President


<PAGE>







                                             GLEACHER/ICG INVESTORS, LLC

                                             By: /s/ Richard Trabulsi
                                                --------------------------------
                                                Name: Richard Trabulsi
                                                Title: Member


<PAGE>





                                   SCHEDULE I

<TABLE>
<CAPTION>

                                                  Number of
Purchasers                        Series of       Preferred     Number of    Purchase Price
                                  Preferred         Shares      Warrants      of the Shares

<S>                               <C>               <C>         <C>           <C>
Liberty Media Corporation         Series A-1        50,000      6,666,667     $500,000,000
HMTF Bridge ICG, LLC              Series A-2        11,500      1,533,334     $115,000,000
HM4 ICG Qualified Fund, LLC       Series A-2        10,464      1,395,253     $104,644,000
HM4 ICG Private Fund, LLC         Series A-2            74          9,885         $741,000
HM PG-IV ICG, LLC                 Series A-2           557         74,281       $5,571,000
HM 4-SBS ICG Coinvestors, LLC     Series A-2           251         33,412       $2,506,000
HM 4-EQ ICG Coinvestors, LLC      Series A-2           154         20,502       $1,538,000
Gleacher/ICG Investors LLC        Series A-3         2,000        266,666      $20,000,000
</TABLE>