<PAGE>
 

                                                                     Exhibit 4.9

                              AMENDMENT NO. 1 TO
                      STOCKHOLDERS AGREEMENT AND CONSENT
                      ----------------------------------


     This Amendment No. 1 to Stockholders Agreement and Consent (the 
"Amendment") is entered into as of this 7th day of July, 1998, among Focal 
Communications Corporation, a Delaware corporation (the "Company") and the 
stockholders listed on the signature page hereof (the "Stockholders"). 
Capitalized terms not otherwise defined in this Agreement are used herein with 
the meanings assigned to such terms in the Stock Purchase Agreement, dated 
November 27, 1996, by and among the parties hereto (the "Stock Purchase 
Agreement").

     WHEREAS, the Company and the Stockholders wish to amend the provisions of 
the Stockholders Agreement, dated November 27, 1996, by and among the parties 
hereto (the "Stockholders Agreement") as provided in paragraph 1 of this 
Amendment;

     WHEREAS, the Stockholders collectively own all of the Institutional
Investor Stock and the Executive Stock, and

     WHEREAS, the Stockholders wish to consent to the amendment (as provided in 
paragraph 1 of this Amendment) for purposes of the Stock Purchase Agreement and 
the Stockholders Agreement;

     NOW, THEREFORE, for good and valuable consideration, the receipt and 
sufficiency of which is hereby acknowledged, the parties to this Amendment 
hereby agree as follows:

     1.   Amendment to Stockholders Agreement. Pursuant to Section 9 of the 
Stockholders Agreement, clause (i) of the first sentence of Section 3(b) of the 
Stockholders Agreement is hereby amended and restated to read in its entirety as
follows:

               "by will or pursuant to applicable laws of descent and 
          distribution,"

          and the last sentence of Section 3(b) of the Stockholders Agreement is
hereby amended and restated to read in its entirety as follows:

          "A Stockholder's "Family Group" means (i) persons related to such
     Stockholder by blood, marriage or adoption, (ii) any trust solely for the
     benefit of such Stockholder and/or the persons described in clause (i), and
     (iii) any limited partnership; limited liability company, limited liability
     partnership or similar entity all of the equity interests of which are held
     by such Stockholder and/or persons described in clause (i) and/or clause
     (ii)."

     2.   Consent.  For all purposes of the Stock Purchase Agreement (including,
without limitation, Section 4C(xii) and 4E thereof), each of the Stockholders 
consents to the amendment set forth in paragraph 1 of this Amendment.
<PAGE>
 
     3. Counterparts. This Amendment may be executed in multiple counterparts, 
each of which shall be an original and all of which taken together shall 
constitute one and the same agreement.

     4. Descriptive Headings. The descriptive headings of this Amendment are 
inserted for convenience only and do not constitute a part of this Amendment.

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


                                       MADISON DEARBORN CAPITAL
--------------------------------       PARTNERS, L.P.
    Brian F. Addy                      By: Madison Dearborn Partners, Its
                                           General Partner
                                       By: Madison Dearborn Partners, Inc., its
                                           General Partner


                                       By:
--------------------------------           -------------------------------------
    John R. Barnicle                   Its: 
                                            ------------------------------------

                                       By:
--------------------------------           -------------------------------------
    Joseph Beatty                      Its: 
                                            ------------------------------------


                        .              BATTERY VENTURES III, L.P.
--------------------------------       By:  Battery Partners III, L.P., its
    Robert C. Taylor, Jr.                   General Partner

                                       By:
                                           -------------------------------------
                                       Its: 
                                            ------------------------------------


                                       FOCAL COMMUNICATIONS CORPORATION

                                       By: /s/ Robert C. Taylor, Jr.
                                           -------------------------------------
                                       Its: President
                                            ------------------------------------


<PAGE>
 
     3.  Counterparts. This Amendment may be executed in multiple counterparts, 
each of which shall be an original and all of which taken together shall 
constitute one and the same agreement.

     4.  Descriptive Headings. The descriptive headings of this Amendment are 
inserted for convenience only and do not constitute a part of this Amendment.

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


                              MADISON DEARBORN CAPITAL
----------------------------  PARTNERS, L.P.
Brian F. Addy                 By: Madison Dearborn Partners, its General Partner
                              By: Madison Dearborn Partners, Inc., its General 
                                  Partner


                             By:     xxxxxxx
---------------------------      ----------------------------     
John R. Barnicle             Its: VP
                                 ----------------------------


                             By:
---------------------------      ----------------------------     
Joseph Beatty                Its: 
                                 ----------------------------


                             BATTERY VENTURES III, L.P.
---------------------------  By: Battery Ventures III, L.P., its General Partner
Robert C. Taylor, Jr.        

                             By:
                                 ----------------------------
                             Its:
                                 ----------------------------

                             FRONTENAC COMPANY


                             By:
                                 ----------------------------
                             Its:
                                 ----------------------------


                             FOCAL COMMUNICATIONS CORPORATION


                             By:
                                 ----------------------------
                             Its:
                                 ----------------------------
<PAGE>
 
     3. Counterparts. This Amendment may be executed in multiple counterparts, 
each of which shall be an original and all of which taken together shall 
constitute one and the same agreement.

     4. Descriptive Headings. The descriptive headings of this Amendment are 
inserted for convenience only and do not constitute a part of this Amendment.

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


                                       MADISON DEARBORN CAPITAL
--------------------------------       PARTNERS, L.P.
    Brian F. Addy                      By: Madison Dearborn Partners, Its
                                           General Partner
                                       By: Madison Dearborn Partners, Inc., its
                                           General Partner


                                       By:
--------------------------------           -------------------------------------
    John R. Barnicle                   Its: 
                                            ------------------------------------

                                       By:
--------------------------------           -------------------------------------
    Joseph Beatty                      Its: 
                                            ------------------------------------


                                       BATTERY VENTURES III, L.P.
--------------------------------       By:  Battery Partners III, L.P., its
    Robert C. Taylor, Jr.                   General Partner

                                       By:  Nuli Fruli
                                           -------------------------------------
                                       Its: Managing Partner
                                            ------------------------------------


                                       FOCAL COMMUNICATIONS CORPORATION

                                       By:                          
                                           -------------------------------------
                                       Its:            
                                            ------------------------------------



<PAGE>
 
 
     3. Counterparts. This Amendment may be executed in multiple counterparts, 
each of which shall be an original and all of which taken together shall 
constitute one and the same agreement.

     4. Descriptive Headings. The descriptive headings of this Amendment are 
inserted for convenience only and do not constitute a part of this Amendment.

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


                                       MADISON DEARBORN CAPITAL
--------------------------------       PARTNERS, L.P.
    Brian F. Addy                      By: Madison Dearborn Partners, Its
                                           General Partner
                                       By: Madison Dearborn Partners, Inc., its
                                           General Partner


                                       By:
--------------------------------           -------------------------------------
    John R. Barnicle                   Its: 
                                            ------------------------------------

                                       By:
--------------------------------           -------------------------------------
    Joseph Beatty                      Its: 
                                            ------------------------------------


                                       BATTERY VENTURES III, L.P.
--------------------------------       By:  Battery Partners III, L.P., its
    Robert C. Taylor, Jr.                   General Partner

                                       By:               
                                           -------------------------------------
                                       Its:                 
                                            ------------------------------------

                                       FRONTENAC COMPANY

                                       By:  James E. Crawford
                                           -------------------------------------
                                       Its: General Parnter 
                                           -------------------------------------

                                       FOCAL COMMUNICATIONS CORPORATION

                                       By:   
                                           -------------------------------------
                                       Its:  
                                            ------------------------------------




<PAGE>
 
                1998 EQUITY PLAN FOR NON-EMPLOYEE DIRECTORS OF
                       FOCAL COMMUNICATIONS CORPORATION

                            PARTICIPATION AGREEMENT
                            -----------------------

          This Participation Agreement ("Participation Agreement") between the
undersigned Non-Employee Director, __________________ ("Director"), and Focal
Communications Corporation (the "Company") is for the Fiscal Year (as
hereinafter defined) commencing January 1, 199__, and is subject to all of the
terms and conditions of the 1998 Equity Plan for Non-Employee Directors of Focal
Communications Corporation (the "Plan").  Capitalized terms not defined herein
have the meanings set forth in the Plan.

          1.   Election of Voluntary Shares.  Pursuant to the Plan, Director may
               ----------------------------                                     
elect to receive up to 100 percent of his or her Retainer and/or Meeting Fees
from the Company in the form of shares of Common Stock by filing a Participation
Agreement in the form hereof on or before the beginning of the Company's Fiscal
Year (as hereinafter defined) (or such other date as may be specified by the
Board). The Director hereby elects to receive (a) _______% of his or her
Retainer, and (b) _______% of his or her Meeting Fees, in the form of Common
Stock in lieu of a cash payment ("Voluntary Shares") in accordance with the
terms of the Plan and as indicated in this Section 1. This election to receive
Voluntary Shares will be effective for the period beginning on January 1 of such
year and ending on the December 31 of such year (a "Fiscal Year"). Except as the
Board may otherwise provide, this election to receive Voluntary Shares is a one-
time election for the applicable Fiscal Year and, unless Director revokes or
changes such election by filing a new Participation Agreement by the due date
specified above, shall apply to each subsequent Fiscal Year. Once an election
has been terminated, another election may not be made effective until the
commencement of the next subsequent full Fiscal Year unless the Board has
otherwise provided.

     2.   Payment of Voluntary Shares.  No later than ten (10) days following
          ---------------------------                                        
the end of an Accounting Period (as defined in the Plan) (the "Issuance Date"),
the Company shall issue to Director a number of Voluntary Shares for the prior
Accounting Period equal to (i) the amount of Director's Retainer and Meeting
Fees for such Accounting Period that Director has elected to receive as
Voluntary Shares divided by (ii) the Market Value per Share on the last day of
such Accounting Period (the "Valuation Date").  If the foregoing formula would
result in the issuance of fractional shares of Common Stock, any such fractional
shares shall be disregarded, and the remaining amount of the Retainer shall be
paid in cash.  The Company shall pay any and all fees and commissions incurred
in connection with the payment of Voluntary Shares to Director.

          3.   Director Acknowledgment and Signature.  Director understands that
               -------------------------------------                            
participation in the Plan is subject to the terms and conditions contained in
the Plan.
<PAGE>
 
          IN WITNESS WHEREOF, Director has executed this Participation Agreement
on the ______ day of _______________________, 199___.


                                   DIRECTOR

 
                                   _____________________________________________
                                                     Signature



          Received and accepted by the Secretary of Focal Communications
Corporation this day of __________, 199___.


                                   _____________________________________________
                                          Signature of the Secretary of
                                          Focal Communications Corporation

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