Document:

<PAGE>

                                                                    Exhibit 10.1
                                                                    ------------

                                Amendment No. 4
                                      to
                         Registration Rights Agreement

     This Amendment No. 4 ("Amendment") to the Registration Rights Agreement
dated as of July 8, 1998, as amended by Amendment No. 1 dated as of February 18,
1999, by Amendment No. 2 dated as of June 30, 1999, and by Amendment No. 3 dated
as of June 30, 1999 (the "Original Agreement"), is made as of August 1, 2000,
among Choice One Communications Inc., a Delaware corporation (the
"Corporation"), and the Holders listed on the signature pages hereto.

     WHEREAS, the Corporation and the initial Investor Holders and Management
Holders entered into the Registration Rights Agreement on July 8, 1998 which
provides for certain rights and obligations of the Corporation and such Holders
with respect to registration of the Common Stock under the Securities Act (and
such agreement has since been amended as described above);

     WHEREAS, the Corporation, a newly formed Delaware corporation that is a
wholly-owned subsidiary of the Corporation ("Newco"), US Xchange, Inc., a
Delaware corporation ("Target"), and Ronald H.  VanderPol, the holder of all of
the issued and outstanding capital stock of Target, have entered into an
Agreement and Plan of Merger as of May 14, 2000 (the "Merger Agreement");

     WHEREAS, upon consummation of the merger under the Merger Agreement in
accordance with the terms and conditions thereof, Target will be merged with and
into Newco, and Target will become a wholly-owned subsidiary of the Corporation
(the "Acquisition");

     WHEREAS, in connection with obtaining financing for the Acquisition, the
Corporation has issued and sold shares of Series A Senior Cumulative Preferred
Stock and warrants to purchase shares of the Corporation's common stock to the
MSDWCP IV Funds (as defined below pursuant to this Amendment) pursuant to the
terms and conditions of the Securities Purchase Agreement dated as of the date
hereof between the MSDWCP IV Funds and the Corporation (the "Securities-
Purchase Agreement"); and

     WHEREAS, the Securities Purchase Agreement requires that the Original
Agreement be amended to provide for registration rights and private placement
assistance on the terms provided for pursuant to this Amendment;

     NOW, THEREFORE, the parties hereto hereby amend the Original Agreement as
follows:

     SECTION 1.  Amendment to Definitions.  (a) Section 1.01 of the Original
Agreement is hereby amended by inserting the following definition before the
definition of "Common Stock":

          "Common Registrable Securities" means Common Stock (including the
          Warrant Shares) and any securities issued directly or indirectly with
          respect to
<PAGE>

                                      -2-

          such Common Stock by way of a split, dividend, or other division of
          securities, or in connection with a combination of securities,
          recapitalization, merger, consolidation, or other reorganization.

          (b) Section 1.01 of the Original Agreement is hereby amended by
     inserting the following definitions before the definition of "Other
     Securities":

          "MSDWCP IV Funds" means, collectively, Morgan Stanley Dean Witter
          Capital Partners IV, L.P., Morgan Stanley Dean Witter Capital
          Investors IV, L.P., and MSDW IV 892 Investors, L.P.

          "Other Distributee Holder" means the recipient of Registrable
          Securities pursuant to a Distribution-In-Kind (as defined in the
          Transaction Agreement) from an Other Holder, so long as such recipient
          becomes a Holder hereunder and such distributed Registrable Securities
          are not then freely tradeable under Rule 144(k) (i.e.  they retain a
          Securities Act legend following such distribution).

          "Other Holder" means Fleet and/or Waller-Sutton.

          (c) Section 1.01 of the Original Agreement is hereby amended by
     inserting the following definition after the definition of "Person":

          "Preferred Registrable Securities" means Preferred Stock and any
          securities issued directly or indirectly with respect to such
          Preferred Stock by way of a split, dividend, or other division of
          securities, or in connection with a combination of securities,
          recapitalization, merger, consolidation, or other reorganization.

          (d) Section 1.01 of the Original Agreement is hereby amended by
     inserting the following definition before the definition of "Public
     Offering":

          "Preferred Stock" means the shares of Series A Senior Cumulative
          Preferred Stock of the Corporation issued to the MSDWCP W Funds
          pursuant to the Securities Purchase Agreement dated as of August 1,
          2000 between the MSDWCP IV Funds and the Corporation.

          (e) The definition of "Registrable Securities" in Section 1.01 of the
     Original Agreement is deleted in its entirety and replaced with the
     following:

          "Registrable Securities" means, collectively, the Common Registrable
          Securities and/or the Preferred Registrable Securities.  As to any
          particular Registrable Securities, such Registrable Securities shall
          cease to be Registrable Securities when they (i) have been effectively
          registered under the Securities Act and disposed of in accordance with
          the registration statement covering them (provided that any
          Registrable Securities exchanged in an exchange offer contemplated in
          Section 2.11(f) shall not cease to be Registrable Securities upon the
          exchange (x) to the extent that such securities cannot be freely
          disposed of by the holder thereof to the public (at one time without
          volume limits) without complying with the prospectus delivery
          requirements of the Securities Act or (y) if, any broker-dealer
<PAGE>

                                      -3-

          that intends to make a market in the securities is an affiliate of the
          Company and so notifies the Company prior to commencement of the
          exchange offer); or (ii) repurchased by the Corporation or otherwise
          have ceased to be outstanding.

          (f) The definition of "Triggering Investor Holders" in Section 1.01 of
     the Original Agreement is deleted in its entirety and replaced with the
     following:

          "Triggering Investor Holders" means (i) Investor Holders holding at
          least 20% in the aggregate of the Common Registrable Securities held
          by all Investor Holders, (ii) any two out of three of MSCP, Fleet and
          Waller-Sutton or (iii) Investor Holders holding at least a majority in
          the aggregate of the Preferred Registrable Securities held by all
          Investor Holders.

          (g) Section 1.01 of the Original Agreement is hereby amended by
     inserting the following definition at the end thereof:

          "Warrant Shares" means the shares of Common Stock deliverable upon
          exercise of the Warrants No. 1, 2 and 3, each dated as of August 1,
          2000, issued by the Corporation to each of the three MSDWCP IV Funds,
          respectively, as adjusted from time to time.

     SECTION 2.  Amendments to Section 2.01 and 2.02.  (a) Section 2.01(a) is
hereby amended by adding "the Other Holders (acting jointly) or" after "(i)" and
before "the Majority Investor Holders" in the third line hereof

          (b) Clause (ii) of the proviso to Section 2.01(a) is hereby amended
     and restated as follows:

          "(ii) the Investor Holders may collectively exercise their rights
          under this Section 2.01 (1) on an unlimited number of occasions with
          respect to registration statements on Form S-3, (2) with respect to
          Common Stock, on not more than five occasions with respect to
          registration statements on Form S-1 (of which one occasion may be
          exercised only by the Other Holders (acting jointly)), and (3) with
          respect to Preferred Stock or Warrant Shares, on not more than two
          occasions with respect to registration statements on Form S-1;"

          (c) Each of Section 2.01(e) and 2.02(b) is hereby amended by adding
     the following proviso, respectively, at the end of Section 2.01(e) and at
     the end of clause (ii) of Section 2.02(b) before "and (iii)":

          ", provided further that so long as any Other Holder (together with
          Registrable Securities then held by its Other Distributee Holders)
          holds at least 75% of the Registrable Securities held by such Other
          Holder as of August 1, 2000, MSCP (and, only as to Registrable
          Securities acquired from MSCP, its Affiliates) shall not be entitled
          to sell Registrable Securities (other than Preferred Stock or
          warrants) pursuant to a registration statement filed pursuant to
          Section 2.01 or under which such Other Holder (or any of its Other
          Distributee Holders) has requested the inclusion of Registrable
          Securities under Section 2.02 unless such
<PAGE>

                                      -4-

          Other Holder (and/or, if applicable, its Other Distributee Holders)
          are permitted to sell under such registration statement an amount of
          Registrable Securities which, taken together with all other
          dispositions by such Other Holder (and its Other Distributee Holders)
          since August 1, 2000, equals or exceeds the lesser of 25% (as
          equitably adjusted for stock splits, stock dividends and other similar
          events) of the Registrable Securities held by such Other Holder on
          August 1, 2000 and the amount requested to be included (it being
          understood that Registrable Securities held by an Other Distributee
          Holder that are freely tradeable under Rule 144(k) will be deemed to
          have been disposed of for purposes of determining whether the 25%
          disposition priority has been satisfied)."

     SECTION 3.  Further Amendments to Section 2.02.  Section 2.02 of the
Original Agreement is hereby amended by (a) adding "and Preferred Stock" after
"Common Stock" and before ", Other Securities" in the fourth line thereof and
(b) adding "and less than 10% of the Preferred Stock outstanding on the date
hereof" after "Common Stock" and before ", give" in the eighth line thereof.  In
addition, clause (x) of clause (b)(ii) of the proviso to Section 2.02 of the
Original Agreement is hereby amended by inserting "of the class being sold"
after "relative number of Registrable Securities" and before "then held".

     SECTION 4.  Amendment to Section 2.04.  Section 2.04(i) of the Original
Agreement is hereby amended by adding "and, in the case of Preferred Registrable
Securities, listing such Preferred Registrable Securities on such national
securities exchange as may be reasonably requested by the lead or managing
underwriters" after "then listed" in the last line thereof.

     SECTION 5.  Amendment to Section 2.08.  Section 2.08 of the Original
Agreement is hereby amended by (a) inserting "(including, for avoidance of
doubt, Preferred Stock or Warrant Shares)" after "Securities" in the third line
thereof and (b) inserting as the last sentence thereof, "It is understood that
(except for Section 2.09) no contractual transfer restrictions apply to or are
binding on either the Preferred Shares or Warrant Shares."

     SECTION 6.  Amendment to Section 2.09.  Section 2.09 of the Original
Agreement is hereby amended by deleting the phrase "underwritten public offering
of Registrable Securities" in the first sentence and replacing it with the
phrase "underwritten public offering of Common Registrable Securities", and by
deleting the parenthetical "(otherwise than through the registered public
offering then being made)" and replacing it with "(otherwise than through the
registered public offering then being made and other than Preferred Stock or
warrants in the case of an underwritten public offering of Common Stock)".
Further, Section 2.09 of the Original Agreement is hereby amended by adding a
sentence at the end thereof, to read as follows: "In addition to the foregoing,
each Investor Holder agrees not to effect any sale, transfer, disposition or
distribution, including any sale under Rule 144 or any distribution-in-kind to
the partners of, or investors in, such Investor Holder, of any Common Stock of
the Corporation within 180 days after the date of the consummation of the
Acquisition."

     SECTION 7.  Amendment to Section 2.10.  Section 2.10 of the Original
Agreement is hereby amended by adding "and less than 5% of the Preferred Stock
outstanding on the date hereof" after "Common Stock" and before ", the" in the
ninth line thereof.
<PAGE>

                                      -5-

     SECTION 8.  Addition of Section 2.11.  The Original Agreement is hereby
amended by inserting the following new Section 2.11:

          "SECTION 2.11.  Private Placements; Amendments to the Certificate of
     Designations.  (a) The Corporation will use its reasonable best efforts to
     cooperate with and assist the Holders, at their request, in the marketing
     by the Holders, at any time and from time to time while any Preferred Stock
     is held by any Holder, of any Preferred Stock (and if a Holder proposes to
     sell Preferred Stock as a unit with Warrants, any such Warrants) of the
     Corporation held by the Holders in any private transaction not requiring
     registration under the Securities Act, including without limitation (i)
     providing reasonable access to the Corporation's books, records,
     properties, offices, officers, employees, accountants, counsel, and other
     agents, (ii) making available senior management of the Corporation for
     participation in analyst, investor and "road show" presentations, and (iii)
     in preparation of a private placement memorandum or other selling or
     marketing materials containing information customarily included in Rule
     144A transactions (the "Selling Materials"), and delivering such customary
     opinions and certificates, executing and delivering such agreements and
     obtaining such comfort letters, as are customarily requested in such
     transactions, in each case in connection with any such sale of Corporation
     securities.

          (b) The Corporation shall be responsible for all expenses incurred in
     connection with such co-operation, assistance and marketing efforts
     contemplated by Section 2.11 (a), including, without limitation, (1) the
     fees, disbursements and expenses of the Corporation's counsel and
     accountants in connection therewith, (2) all expenses in connection with
     the preparation and printing of all Selling Materials and amendments and
     supplements thereto and the mailing and delivering of copies thereof to any
     placement agents and other intermediaries, (3) the cost of preparing and
     printing or producing any agreements with placement agents or other
     intermediaries involved in such private placement transaction and any blue
     sky or legal investment memoranda, any selling agreements and any other
     documents in connection with the offering, sale or delivery of the
     securities to be disposed of, (4) all expenses in connection with the
     qualification of the securities to be disposed of for offering and sale
     under state securities laws, including the fees and disbursements of
     counsel for the placement agents or other intermediaries or the Holders of
     securities in connection with such qualification and in connection with any
     blue sky and legal investment surveys, (5) transfer agents' and registrars'
     fees and expenses and the fees and expenses of any other agent or trustee
     appointed in connection with such transaction, (6) all security engraving
     and security printing expenses, (7) the legal fees and expenses of one
     counsel for the Holders in connection with any marketing efforts requested
     by a Holder pursuant to Section 2.11, (8) any other fees and disbursements
     of placement agents or other intermediaries customarily paid by the issuers
     of securities, but excluding placement or selling fees and commissions and
     transfer taxes, if any, (9) the costs and expenses of the Corporation
     relating to analyst or investor presentations or any "road show" undertaken
     in connection with the marketing of any such securities, and (10) other
     reasonable out-of-pocket expenses of Holders in connection therewith.
     Notwithstanding the foregoing, each Holder and the Corporation shall be
     responsible for its own internal administrative and similar costs.
<PAGE>

                                      -6-

          (c) The Corporation agrees to indemnify and hold harmless each Holder
     and each person, if any, who controls each Holder within the meaning of
     either Section 15 of the Securities Act or Section 20 of the Securities
     Exchange Act from and against any and all losses, claims, damages and
     liabilities (including, without limitation, any legal or other expenses
     reasonably incurred in connection with defending or investigating any such
     action or claim) insofar as such losses, claims, damages or liabilities are
     caused by any untrue statement or alleged untrue statement of a material
     fact contained in any such Selling Materials or caused by any omission or
     alleged omission to state therein a material fact required to be stated
     therein or necessary to make the statements therein not misleading, except
     insofar as such losses, claims, damages or liabilities are caused by any
     such untrue statement or omission or alleged untrue statement or omission
     based upon information relating to a Holder furnished to the Corporation in
     writing by a Holder expressly for use therein.  The Holders agree to
     indemnify and hold harmless the Corporation and each person who so controls
     the Corporation to the same extent as the foregoing indemnity by the
     Corporation of the Holders and persons so controlling the Holders but only
     with reference to information relating to a Holder furnished to the
     Corporation in writing by a Holder expressly for use therein.  The
     provisions and procedures set forth in Section 2.06 shall apply in the case
     of any indemnification claim made under the foregoing provisions of this
     Section 2.11(c).

          (d) To the extent that indemnification under Section 2.11(c) is
     unavailable for any reason or insufficient to hold any indemnified party
     harmless, the indemnifying party will contribute to the amount paid or
     payable by the indemnified party, in such proportion as is appropriate to
     reflect the relative fault of the indemnifying party or parties on the one
     hand and of the indemnified party or parties on the other hand in
     connection with the statements or omissions that resulted in the losses,
     claims, damages or liabilities (with such relative fault to be determined
     by reference to, among other things, whether the untrue or alleged untrue
     statement of a material fact or the omission or alleged omission to state a
     material fact relates to information supplied by the Corporation or by a
     Holder and the parties' relative intent, knowledge, access to information
     and opportunity to correct or prevent such statement or omission), and any
     other relevant equitable considerations.

          (e) If requested by the Holders holding a majority in aggregate of the
     Preferred Stock, the Corporation shall use its best efforts to amend the
     Certificate of Designations, Preferences and Rights of the Preferred Stock
     to the extent reasonably necessary or useful to (i) facilitate the public
     trading of the Preferred Stock and (ii) permit the listing of the Preferred
     Stock on a securities exchange in accordance with the rules of such
     securities exchange as in effect on such time.

          (f) (A) Without limiting the foregoing provisions of this Section
     2.11, in the event any Preferred Stock is sold to one or more purchasers in
     a private placement under Rule 144A under the Securities Act and the intent
     of the parties in such sale is that such Preferred Stock subsequently be
     exchanged for substantially similar shares of preferred stock of the
     Corporation that have been registered under the Securities Act pursuant to
     an exchange offer made by the Corporation to such purchasers registered on
     Form S-4 (such transaction sometimes referred to as an "Exxon Capital" or
     analogous exchange offer),
<PAGE>

                                      -7-

     then the Corporation shall take any and all of the following actions as are
     reasonably requested by Holders holding a majority in aggregate of the
     Preferred Stock:

          (i)  promptly register under the Securities Act on Form S-4 shares of
          preferred stock of the Corporation having substantially the same terms
          as the Preferred Stock in order to execute the exchange offer
          described above, cause such registration statement to become effective
          as soon as practicable, and commence and execute such exchange offer
          promptly thereafter in accordance with applicable securities and
          tender offer laws, rules and regulations and consistent with custom
          and market practice for such transactions; and

          (ii)  enter into such additional and ancillary agreements, documents
          and instruments as are necessary, desirable or customary for and to
          implement such transaction, including without limitation a certificate
          of designation for the new shares of preferred stock, and
          (notwithstanding Section 2.10 or 3.03) an amendment to this Agreement
          or a separate registration rights agreement providing for (x)
          customary registration rights provisions to the purchasers in such
          private placement reflecting the foregoing and, if requested by such
          purchasers, providing for customary time periods for filing of such
          Form S-4 and commencement of the exchange offer and reasonable and
          customary liquidated damages for failure to meet such time periods,
          and (y) an obligation to register the Preferred Stock shares on a
          shelf registration on Form S-1 (or Form S-3, to the extent the
          Corporation is eligible) for so long as the shares are outstanding in
          the event that the Holders of a majority of the Preferred Stock
          immediately prior to the private placement notify the Corporation
          prior to consummation of the exchange offer that any broker-dealer (an
          "Affiliated Market Maker") that intends to make a market in the
          securities may be an affiliate of the Corporation as defined in the
          rules and regulations of the Securities and Exchange Commission.

               (B) In the event that (i) at any time the Holders holding a
          majority in aggregate of the Preferred Stock determine to sell
          Warrants as a unit with Preferred Stock in a transaction as described
          in Section 2.11(f)(A) or determine not to pursue a transaction as
          described in Section 2.11(f)(A) or (ii) at any time the Securities and
          Exchange Commission determines that an exchange offer as described in
          Section 2.11(f)(A) is not permitted, then the Corporation shall, at
          the request of Holders holding a majority in aggregate of the
          Preferred Stock, promptly register the requested shares of Preferred
          Stock (and/or, if applicable, Warrants) on a shelf registration on
          Form S-1 (or Form S-3, to the extent the Corporation is eligible) and
          keep the registration effective for so long as any securities covered
          thereby constitute Registrable Securities (but for this purpose
          securities will be deemed to cease being Registrable Securities where
          they have been sold pursuant to Rule 144(k) and are thereafter freely
          saleable by the purchaser without any volume or other resale
          restriction and without any Securities Act legend imprinted on the
          stock certificate).
<PAGE>

                                      -8-

               (C) Notwithstanding anything else contained herein, (x) no Holder
          will have any "piggyback" or other right to require registration of
          Registrable Securities on such Form S-4 (which will not limit the
          Holders' rights to require registration under Section 2.01 or 2.02 to
          the extent provided for therein), and (y) although not a registration
          requested pursuant to Section 2.01 (including, for example, for
          purposes of Section 2.01 (a)(v)), such a registration contemplated in
          this Section 2.11 on Form S-4 (or Form S-1 or S-3) will, as
          appropriate, be treated as though requested under Section 2.01 for
          purposes of Section 2.03 {expenses}, 2.04 {procedures}, and 2.06
          {indemnity} (it being understood that for this purpose Section 2.06
          will be construed as though each exchanging purchaser, selling holder
          and Affiliated Market Maker were a Selling Holder).

          (g) Nothing contained in this Section 2.11 and no performance by the
     Corporation of its obligations under this Section 2.11 shall in any way
     limit or reduce the rights of any Holder under Section 2.01 or Section
     2.02."

     SECTION 9.  Other Defined Terms.  Capitalized terms used in this Amendment
and not otherwise defined have the meanings ascribed to them in the Original
Agreement.

     SECTION 10.  Effect of Amendment; Governing Law.  Except as amended hereby,
the Original Agreement shall remain unchanged.  The Original Agreement, as
amended hereby, shall remain in full force and effect.  This Amendment shall be
governed by, and construed under, the laws of the State of Delaware, all rights
and remedies being governed by said laws, without regard to conflict of laws
principles.

     SECTION 11.  Counterparts.  This Amendment may be executed simultaneously
in two or more counterparts, any one of which need not contain the signatures of
more than one party, but all such counterparts taken together shall constitute
one and the same agreement.

     IN WITNESS WHEREOF, the parties hereto have executed this Amendment as of
the date first written above.

                                    CHOICE ONE COMMUNICATIONS INC.

                                    By:  /s/ Steve M. Dubnik
                                         ---------------------------------

                                    Its:  Chairman and CEO
                                          --------------------------------

                                    MANAGEMENT HOLDERS

                                    /s/ Steve M. Dubnik
                                    --------------------------------------
                                    Steve M. Dubnik, as a Management Member and
                                    as Chief Executive Officer of Choice One
                                    Communications Inc.

                                    /S/ Mae Squier-Dow
                                    ------------------
<PAGE>

                                      -9-

                                    Mae Squier-Dow

                                    /S/ Kevin Dickens
                                    -----------------
                                    Kevin Dickens

                                    _________________________________________
                                    Phillip Yawman

                                    _________________________________________
                                    Joseph Schaal

                                    _________________________________________
                                    Elizabeth Ellis

                                    _________________________________________
                                    Joseph Calzone

                                    ________________________________________
                                    Michelle Paroda

                                    _________________________________________
                                    Linda Chapman

                                    _________________________________________
                                    John Zimmer

                                    _________________________________________
                                    David Fitts

                                    _________________________________________
                                    Kenneth Okolowicz

                                    _________________________________________
                                    Daniel K. Iles

                                    _________________________________________
                                    Michael D'Angelo

                                    _________________________________________
                                    Robert Merrill
<PAGE>

                                      -10-

                                    -----------------------------------------
                                    Kim Scovill

                                    INVESTOR HOLDERS

                                    MORGAN STANLEY CAPITAL PARTNERS III, L.P.

                                    By:  MSCP III, LLC, its general partner
                                    By:  Morgan Stanley Capital Partners III,
                                         Inc., its Member

                                    By:  /s/ John Ehrenkranz
                                         ------------------------------------

                                    Its:  Managing Director
                                          -----------------------------------

                                    By:   ___________________________________

                                    Its:  ___________________________________

                                    MSCP III 892 INVESTORS, L.P.

                                    By:  MSCP III, LLC, its general partner
                                    By:  Morgan Stanley Capital Partners III,
                                         Inc., its Member

                                    By:  /s/ John Ehrenkranz
                                         ------------------------------------

                                    Its: ___________________________________

                                    By:  ___________________________________

                                    Its: ___________________________________
<PAGE>

                                      -11-

                                    MORGAN STANLEY CAPITAL INVESTORS, L.P.

                                    By:  MSCP III, LLC, its general partner
                                    By:  Morgan Stanley Capital Partners III,
                                         Inc., its Member

                                    By:  /s/ John Ehrenkranz
                                         -------------------------------------

                                    Its: _____________________________________

                                    By:  _____________________________________

                                    Its: _____________________________________

                                    MORGAN STANLEY DEAN WITTER CAPITAL PARTNERS
                                    IV, L.P.

                                    By:  MSDW Capital Partners IV, LLC, its
                                         general partner
                                    By:  MSDW Capital Partners IV, Inc., its
                                         Member

                                    By:  /s/ John Ehrenkranz
                                         -------------------------------------

                                    Its: _____________________________________

                                    By:  _____________________________________

                                    Its: _____________________________________

                                    MSDW IV 892 INVESTORS, L.P.

                                    By:  MSDW Capital Partners IV, LLC, its
                                         general partner
                                    By:  MSDW Capital Partners IV, Inc., its
                                         Member

                                    By:  /s/ John Ehrenkranz
                                         -------------------------------------

                                    Its: _____________________________________

                                    By:  _____________________________________

                                    Its: _____________________________________
<PAGE>

                                      -12-

                                    MORGAN STANLEY DEAN WITTER CAPITAL INVESTORS
                                    IV, L.P.

                                    By:  MSDW Capital Partners IV, LLC, its
                                         general partner
                                    By:  MSDW Capital Partners IV, Inc., its
                                         Member

                                    By:  /s/ John Ehrenkranz
                                         --------------------------------------

                                    Its:  _____________________________________

                                    By:   _____________________________________

                                    Its:  _____________________________________

                                    CHISHOLM PARTNERS III, L.P.

                                    By:  Silverado III, L.P., its General
                                         Partner
                                    By:  Silverado III Corp., its General
                                         Partner

                                    By:  /s/ Robert M. Van Degna
                                         ---------------------------------------
                                         Robert M. Van Degna
                                         Chairman & CEO
<PAGE>

                                      -13-

                                    KENNEDY PLAZA PARTNERS

                                    By:  /s/ Robert M. Van Degna
                                         ---------------------------------------
                                         Robert M. Van Degna
                                         Managing General Partner

                                    FLEET VENTURE RESOURCES, INC.

                                    By:  /s/ Robert M. Van Degna
                                         --------------------------------------
                                         Robert M. Van Degna
                                         Chairman & CEO

                                    FLEET EQUITY PARTNERS VI, L.P.

                                    By:  Fleet Growth Resources H, Inc., its
                                         General Partner

                                    By:  /s/ Robert M. Van Degna
                                         ---------------------------------------
                                         Robert M. Van Degna
                                         Chairman & CEO

                                    WALLER-SUTTON MEDIA PARTNERS, L.P.

                                    By:  Waller Sutton Media, L.L.C. its general
                                         partner

                                    By:  /s/ Bruce Hernandez
                                         ---------------------------------------
                                       Bruce Hernandez
                                       Chief Executive Officer

                                    FIRST UNION CAPITAL PARTNERS, INC.

                                    By: ________________________________________

                                    Its: _______________________________________
<PAGE>

                                      -14-

                                    GENERAL ELECTRIC CAPITAL CORPORATION

                                    By: ________________________________________

                                    Its: _______________________________________

                                    CARAVELLE INVESTMENT FUND, L.L.C.

                                    By:  Caravelle Advisors, L.L.C., as
                                         Investment Manager and Attorney in Fact

                                    By: ________________________________________

                                    Its: _______________________________________

                                    ROYCE J. HOLLAND

                                    ____________________________________________
                                    Royce J. Holland

                                    R. PHILIP SILVER

                                    ____________________________________________
                                    R. Philip Silver<PAGE>

                                                                    Exhibit 10.2
                                                                    ------------

                                Amendment No. 7
                                      to
                             Transaction Agreement

     This Amendment No. 7 ("Amendment") to the Transaction Agreement dated as of
July 8, 1998, as amended by Amendment No. 1 dated as of December 18, 1998, by
Amendment No. 2 dated as of February 18, 1999, by Amendment No. 3 dated as of
May 14, 1999, by Amendment No. 4 dated as of June 30, 1999, by Amendment No. 5
dated as of June 30, 1999, and by Amendment No. 6 dated as of November 18, 1999
(the "Original Agreement"), is made as of August 1, 2000, among Choice One
Communications Inc. (the "Corporation") and the persons listed on the signature
pages hereto.

     WHEREAS, the Corporation, a newly formed Delaware corporation that is a
wholly-owned subsidiary of the Corporation ("Barter Acquisition Corporation"),
US Xchange, Inc., a Delaware corporation ("Target"), and Ronald H. Vander Pol,
the holder of all of the issued and outstanding capital stock of Target, have
entered into an Agreement and Plan of Merger as of May 14, 2000 (the "Merger
Agreement");

     WHEREAS, upon consummation of the merger (the "Merger") under the Merger
Agreement in accordance with the terms and conditions thereof, Target will be
merged with and into Barter Acquisition Corporation, and Target will become a
wholly-owned subsidiary of the Corporation (the "Acquisition");

     WHEREAS, in connection with obtaining financing for the Acquisition, the
Corporation will issue and sell Series A Senior Cumulative Preferred Stock and
warrants to purchase shares of the Corporation's common stock substantially on
the terms set forth in a commitment letter dated April 27, 2000 between MSDWCP
IV and the Corporation;

     WHEREAS, Section 6.19 of the Merger Agreement contemplates that the
Original Agreement will be amended to provide for a Board seat for a designee of
Ronald H. VanderPol on the terms specified below; and

     WHEREAS, the parties desire to amend the Original Agreement to provide for
certain governance arrangements to be effective upon consummation of the Merger;

     NOW, THEREFORE, the parties hereto hereby agree as follows:

     SECTION 1.    Amendments to Section 5.03. (a) Section 5.03(a) is hereby
amended by deleting "seven" and replacing it with "eleven".

          (b) Section 5.03(b) is hereby amended by (1) deleting "and" after the
     semicolon at the end of clause (iii), (2) inserting "; and" at the end of
     clause (iv) before the period, and (3) inserting thereafter the following
     new clause (v):
<PAGE>

                                      -2-

          "(v)  Richard Postma (or other designee of Ronald H. Vander Pol
          approved by the Board of Directors, which approval shall not be
          unreasonably withheld) shall be designated as a director so long as
          Ronald H. Vander Pol beneficially owns at least 4,500,000 shares of
          Common Stock."

     SECTION 2.  Amendment to Definitions. (a)  The Original Agreement is hereby
amended by inserting the following definition before the definition of
"Subsidiary":

          "Preferred Stock" means any Series A Senior Cumulative Preferred Stock
          of the Corporation issued to MSDWCP IV to obtain financing for the
          Acquisition as contemplated in the commitment letter dated April 27,
          2000 between the Corporation and MSDWCP IV.

          (b) The definition of "MSCP Equity" in the Original Agreement is
     hereby amended by inserting the following new sentence at the end thereof:

          "Notwithstanding the foregoing, in order to facilitate Morgan Stanley
          Dean Witter Capital Partners IV, L.P.'s status as a "venture capital
          operating company" (for purposes of the "plan asset" regulations
          published by the Department of Labor in relation to pension and other
          plans subject to the Employee Retirement Income Security Act of 1974,
          as amended), in the event any Preferred Stock is issued to MSDWCP IV
          in connection with the Acquisition, such Preferred Stock will be
          deemed MSCP Equity for purposes of Section 5.03 (the intent being
          that, without limiting the rights provided for under Section
          5.03(b)(i) by virtue of Common Stock ownership, Morgan Stanley Dean
          Witter Capital Partners IV, L.P. will be entitled to designate at
          least one director so long as it holds at least 10% of the Preferred
          Stock initially issued to it)."

     SECTION 3.  Other Defined Terms. Capitalized terms used in this Amendment
and not otherwise defined have the meanings ascribed to them in the Original
Agreement.

     SECTION 4.  Effectiveness; Effect of Amendment, Governing Law.  The
amendment to Section 5.03 effected by Section 1 hereof and the amendment to
Definitions effected by Section 2 hereof shall be not effective until
consummation of the Merger. Except as amended hereby, the Original Agreement
shall remain unchanged. The Original Agreement, as amended hereby, shall remain
in full force and effect. This Amendment shall be governed by, and construed
under, the laws of the State of Delaware, all rights and remedies being governed
by said laws, without regard to conflict of laws principles.

     SECTION 5.  Counterparts.  This Amendment may be executed simultaneously in
two or more counterparts, any one of which need not contain the signatures of
more than one party, but all such counterparts taken together shall constitute
one and the same agreement.
<PAGE>

                                      -3-

     IN WITNESS WHEREOF, the parties hereto have executed this Amendment as of
the date first written above.

                                    CHOICE ONE COMMUNICATIONS INC.

                                    By:  /s/ Steve M. Dubnik
                                         -------------------------------------

                                    Its:  Chairman and Chief Executive Officer
                                          ------------------------------------

                                    MANAGEMENT MEMBERS

                                    /s/ Steve M. Dubnik
                                    ------------------------------------------
                                    Steve M. Dubnik, as a Management Member and
                                    as Chief Executive Officer of Choice One
                                    Communications, Inc.

                                    /s/ Mae Squier - Dow
                                    ------------------------------------------
                                    Mae Squier-Dow

                                    /s/ Kevin Dickens
                                    ------------------------------------------
                                    Kevin Dickens

                                    /s/ Philip Yawman
                                    ------------------------------------------
                                    Philip Yawman

                                    /s/ Ajay Sabherwal
                                    ------------------------------------------
                                    Ajay Sabherwal

                                    /s/ Joseph Schaal
                                    ------------------------------------------
                                    Joseph Schaal

                                    /s/ Elizabeth Ellis
                                    ------------------------------------------
                                    Elizabeth Ellis

                                    /s/ Joseph Calzone
                                    ------------------------------------------
                                    Joseph Calzone

                                    /s/ Michelle Paroda
                                    ------------------------------------------
                                    Michelle Paroda

                                    /s/ Linda Chapman
                                    ------------------------------------------
                                    Linda Chapman
<PAGE>

                                      -4-

                                    __________________________________________
                                    John Zimmer

                                    __________________________________________
                                    David Fitts

                                    /s/ Kenneth Okolowicz
                                    ------------------------------------------
                                    Kenneth Okolowicz

                                    __________________________________________
                                    Daniel K. Iles

                                    __________________________________________
                                    Michael D'Angelo

                                    /s/ Robert Merrill
                                    ------------------------------------------
                                    Robert Merrill

                                    /s/ Kim Robert Scovill
                                    ------------------------------------------
                                    Kim Robert Scovill

                                    /s/ Robert Bailey
                                    ------------------------------------------
                                    Robert Bailey

                                    /s/ James Currie
                                    ------------------------------------------
                                    James Currie

                                    /s/ Scott Deverell
                                    ------------------------------------------
                                    Scott Deverell

                                    __________________________________________
                                    Paul Cissel

                                    __________________________________________
                                    Eric Peterson

                                    /s/ Pam Huber - Hauck
                                    ------------------------------------------
                                    Pam Huber-Hauck

                                    __________________________________________
                                    Carla Vaccaro

<PAGE>

                                      -5-

                                    __________________________________________
                                    Nancy Farrell

                                    INVESTOR MEMBERS

                                    MORGAN STANLEY CAPITAL
                                    PARTNERS III, L.P.

                                    By:  MSCP III, LLC, its general partner
                                    By:  Morgan Stanley Capital Partners III,
                                         Inc., its Member

                                    By:   /s/ John Ehrenkranz
                                          --------------------------------------

                                    Its:  Managing Director
                                          --------------------------------------

                                    By:   ______________________________________

                                    Its:  ______________________________________

                                    MSCP III 892 INVESTORS, L.P.

                                    By:  MSCP III, LLC, its general partner
                                    By:  Morgan Stanley Capital Partners III,
                                         Inc., its Member

                                    By:   /s/ John Ehrenkranz
                                          --------------------------------------

                                    Its:  ______________________________________

                                    By:   ______________________________________

                                    Its:  ______________________________________
<PAGE>

                                      -6-

                                    MORGAN STANLEY CAPITAL
                                    PARTNERS III, L.P.

                                    By:  MSCP III, LLC, its general partner
                                    By:  Morgan Stanley Capital Partners III,
                                         Inc., its Member

                                    By:  /s/ John Ehrenkranz
                                         ---------------------------------------

                                    Its: _______________________________________

                                    By:  _______________________________________

                                    Its: _______________________________________

                                    MORGAN STANLEY DEAN WITTER CAPITAL PARTNERS
                                    IV, L.P.

                                    By:  MSDW Capital Partners IV, LLC, its
                                         general partner
                                    By:  MSDW Capital Partners IV, Inc., its
                                         Member

                                    By:  /s/ John Ehrenkranz
                                         ---------------------------------------

                                    Its: _______________________________________

                                    By:  _______________________________________

                                    Its: _______________________________________
<PAGE>

                                      -7-

                                    MSDW IV 892 INVESTORS, L.P.

                                    By:  MSDW Capital Partners IV, LLC,
                                         its general partner
                                    By:  MSDW Capital Partners IV,
                                         Inc., its Member

                                    By:  /s/ John Ehrenkranz
                                         ---------------------------------------

                                    Its: _______________________________________

                                    By:  _______________________________________

                                    Its: _______________________________________

                                    MORGAN STANLEY DEAN WITTER CAPITAL PARTNERS
                                    IV, L.P.

                                    By:  MSDW Capital Partners IV, LLC, its
                                         general partner
                                    By:  MSDW Capital Partners IV,
                                         Inc., its Member

                                    By:  /s/ John Ehrenkranz
                                         ---------------------------------------

                                    Its: _______________________________________

                                    By:  _______________________________________

                                    Its: _______________________________________

                                    CHISHOLM PARTNERS III, L.P.

                                    By:  Silverado III, L.P., its General
                                         Partner
                                    By:  Silverado III Corp., its General
                                         Partner

                                    By:  /s/ Robert M. Van Degna
                                         ---------------------------------------
                                         Robert M. Van Degna
                                         Chairman & CEO
<PAGE>

                                      -8-

                                    KENNEDY PLAZA PARTNERS

                                    By:  /s/ Robert M. Van Degna
                                         ---------------------------------------
                                         Robert M. Van Degna
                                         Chairman & CEO

                                    FLEET VENTURE RESOURCES, INC.

                                    By:  /s/ Robert M. Van Degna
                                         ---------------------------------------
                                         Robert M. Van Degna
                                         Chairman & CEO

                                    FLEET EQUITY PARTNERS VI, L.P.

                                    By:  Fleet Growth Resources II, Inc., its
                                         General Partner

                                    By:  /s/ Robert M. Van Degna
                                         ---------------------------------------
                                         Robert M. Van Degna
                                         Chairman & CEO

                                    WALLER-SUTTON MEDIA PARTNERS, L.P.

                                    By:  Waller Sutton Media, L.L.C., its
                                         general partner

                                    By:  /s/ Bruce Hernandez
                                         ---------------------------------------
                                         Bruce Hernandez

                                    FIRST UNION CAPITAL PARTNERS, INC.

                                    By:  _______________________________________

                                    Its: _______________________________________

                                    GENERAL ELECTRIC CAPITAL CORPORATION

                                    By:  _______________________________________

                                    Its: _______________________________________
<PAGE>

                                      -9-

                                    CARAVELLE INVESTMENT FUND, L.L.C.

                                    By:  Caravelle Advisors, L.L.C., as
                                         Investment Manager and Attorney In Fact

                                    By:  _______________________________________

                                    Its: _______________________________________

                                    ROYCE J. HOLLAND

                                    __________________________________________
                                    Royce J. Holland

                                    R. PHILIP SILVER

                                    __________________________________________
                                    R. Philip Silver

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