Exhibit 10.1

                               VIALOG CORPORATION



                                February 25, 2000



            Re: Exchange Offer for the Company's 12-3/4% Senior Notes

Dear Noteholder:

         This letter  agreement (the "Letter  Agreement"),  dated as of the date
first  written  above,  by  and  between  Vialog  Corporation,  a  Massachusetts
corporation (the "Company"), and you (referred herein as either the "Noteholder"
or the "Holder") is entered into in connection  with a proposed  exchange  offer
for the Company's 12-3/4% Senior Notes due 2001 (the "Notes").

         As previously disclosed to the Holder, the Company is in the process of
implementing  a strategic  plan that includes an exchange  offer (the  "Exchange
Offer") on the terms and  conditions  set forth in the Summary of Proposed Terms
(the "Summary of Terms") attached as Exhibit A. If completed, the Exchange Offer
will allow  Noteholders  to  receive,  prior to  maturity  of the Notes,  both a
significant  amount  of  cash  and a new  series  of the  Company's  convertible
preferred stock. The Company's current  willingness to proceed with the Exchange
Offer is contingent upon receiving  signed Letter  Agreements from Holders of at
least 95% of the  aggregate  principal  amount of the  outstanding  Notes.  This
condition may, however, be waived by the Company in its sole discretion.

         Based upon and subject to the foregoing, the parties agree as follows:

         1.  Commencement  of Exchange  Offer.  The Company  will  commence  the
Exchange  Offer  as soon as  practicable  following  receipt  of  signed  Letter
Agreements from Holders of at least 95% of the aggregate principal amount of the
outstanding  Notes and approval of the terms of the proposed  Exchange  Offer by
the Company's Board of Directors;  provided, however, that the Company shall not
be obligated to commence the Exchange Offer if (i) signed Letter Agreements from
Holders of at least 95% of the  aggregate  principal  amount of the  outstanding
Notes are not received by the close of business on February  28, 2000;  (ii) the
Company is unable to obtain  financing for the Exchange Offer; or (iii) approval
of the Company's Board of Directors is not obtained.

         2. Agreements of  Noteholders.  The Noteholder  agrees that,  following
receipt  from the  Company of formal  Exchange  Offer and  Consent  Solicitation
documents  incorporating  the Summary of Terms  attached  hereto (the  "Exchange
Offer  Documents")  and  otherwise  acceptable  in  form  and  substance  to the
Noteholder  and its advisors,  it will take such actions as may be necessary (i)
to cause its consent to be given to the amendment of certain covenants contained
in the  indenture  governing the Notes,  as may be proposed by the Company,  and
(ii) to cause all of its Notes to be tendered  prior to the  initial  Expiration
Date set forth in the  Exchange  Offer  Documents  in exchange  for cash and the
Company's convertible pay-in-kind preferred stock as described in the Summary of
Terms. The Noteholder acknowledges that in the event that less than a 95% tender
occurs, the Exchange Offer may be implemented through a pre-packaged  bankruptcy
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plan and  agrees to consent to and  support  such a plan on terms  substantially
identical to the Exchange Offer, if proposed by the Company. The Noteholder also
agrees not to sell or  transfer  any or all of such  Holder's  Notes  unless the
transferee (the  "Transferee")  of such Notes agrees to be bound by the terms of
this Letter Agreement prior to such transfer.

         3.  Disclosure.  The parties to this  Letter  Agreement  authorize  the
Company to disclose in the Exchange  Offer  Documents the existence and terms of
this Letter Agreement.

         4. Termination.  This Letter Agreement shall terminate upon the earlier
of (i) 30 days  from the  date  hereof,  if by that  date  the  Company  has not
obtained a written  commitment  for the financing  necessary to  consummate  the
Exchange  Offer,  (ii) April 15, 2000, if the Exchange Offer  Documents have not
been  distributed by that date,  (iii) the  termination of the Exchange Offer by
the Company or (iv) June 30, 2000.

         5.  GOVERNING  LAW.  THIS LETTER  AGREEMENT  SHALL BE GOVERNED  BY, AND
CONSTRUED IN ACCORDANCE  WITH, THE LAWS OF THE STATE OF NEW YORK,  REGARDLESS OF
THE LAWS THAT MIGHT OTHERWISE GOVERN UNDER APPLICABLE PRINCIPLES OF CONFLICTS OF
LAWS THEREOF.

         6. Enforcement.  Irreparable  damages would occur in the event that any
of the provisions of this Letter Agreement were not performed in accordance with
their specific terms or were otherwise breached.  Accordingly, the parties shall
be entitled to an injunction or injunctions  to prevent  breaches of this Letter
Agreement and to enforce  specifically  the terms and  provisions of this Letter
Agreement in the federal courts of the United States located in the State of New
York,  this being in addition to any other  remedy to which they are entitled at
law or in equity.

         7.  Further  Assurances.  Holder  shall  execute and deliver such other
documents and  instruments  and take such further actions as may be necessary or
appropriate or as may be reasonably  requested by the Company in connection with
the Exchange Offer.

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

         9. No Waiver.  Except as expressly  provided in this Letter  Agreement,
the Holders are not waiving any defaults or other rights, and reserve all rights
and remedies they may have, under the Indenture (as defined in Exhibit A and the
Notes).

         10. Legal Fees. The Company agrees to pay the reasonable legal fees and
disbursements  of Debevoise & Plimpton,  counsel to the  unofficial  Noteholders
Committee.

                                * * * * * * * * *
<PAGE>

          If  the  foregoing  accurately  reflects  our  understanding,   please
indicate  your  acceptance  by signing a copy of this letter and returning it to
the undersigned.

                                      VIALOG CORPORATION


                                      By:    _____________________________
                                             Name:
                                             Title:



ACCEPTED AND AGREED TO:




Print Name: ____________________

By: ___________________________              Principal Amount of Notes:_________
         Name:                               Address for Notices:
         Title:                              ___________________________________
                                             ___________________________________
                                             ___________________________________

<PAGE>
                                                             Exhibit A to Letter
                                              Agreement dated February ___, 2000


                            Summary of Proposed Terms


                                   {Attached}





<PAGE>
                            SUMMARY OF PROPOSED TERMS

                  $16,500,000 CONVERTIBLE PIK PREFERRED SHARES


                        Issuer:         "Vialog Corporation" the ("Company").

                         Issue:         Convertible PIK Preferred Shares (the
                                        "Preferred Shares").

                        Amount:         $16,500,000

                   Issue Price:         $__ per share.

                Final Maturity:         6 years.

        Liquidation Preference:         $100 per share plus accrued and unpaid
                                        dividends.

                     Dividends:         8.00%, payable semi-annually. In the
                                        event dividends are not paid in cash,
                                        the dividends will be paid in additional
                                        Preferred Shares.

                       Ranking:         The Preferred Shares will rank senior to
                                        the  Company's  common  stock and common
                                        and preferred  stock  dividends and will
                                        rank  senior to any  class of  preferred
                                        shares issued after the closing date.

            Nature of Offering:         Private placement to qualified
                                        institutional buyers without
                                        registration under the Securities Act of
                                        1933, as amended.

                 Call Features:         The Preferred Shares shall be callable
                                        at any time at a price in accordance
                                        with the schedule below:

                                        |X|      Year 1 - 101%
                                        |X|      Year 2 - 102%
                                        |X|      Year 3 - 103%
                                        |X|      Years 4 - 6 @ par
<PAGE>
            Conversion Feature:         The holder of any Preferred Share has
                                        the right, upon delivery of written
                                        notice to the Company and surrender of
                                        the certificate for such share, to
                                        convert such Preferred Share into common
                                        shares in the manner described below.
                                        Each Preferred Share is convertible into
                                        the number of fully paid common shares
                                        as is obtained by (i) multiplying the
                                        number of the Preferred Shares so to be
                                        converted by $100.00 and adding
                                        aggregate "paid in kind" dividends on
                                        such shares as of the date of the
                                        conversion, and (ii) dividing the result
                                        by the Conversion Price. The Conversion
                                        Price will be equal to the lesser of $8
                                        per share or 150% of the average closing
                                        price of the Company's common stock for
                                        the 20 trading days prior to closing,
                                        ("market price").

        Adjustment of Preferred         On the first anniversary of the closing,
        Share Conversion Price:         the conversion price may be adjusted
                                        (only downward) as follows; if the
                                        "market price" of the Company's common
                                        stock falls below the "market price"
                                        established at closing, then the
                                        conversion price in effect will be
                                        adjusted proportionately to reflect the
                                        percentage decline in the "market
                                        price." For example, if the "market
                                        price" at close is $6 per share, then
                                        the conversion price will be set at $8.
                                        On the first anniversary, if the "market
                                        price" is $5 per share (a 16.67%
                                        decline) then the conversion price will
                                        be adjusted downward by 16.67% to
                                        establish a new conversion price of
                                        $6.67. This option will be exercisable
                                        only once, on the first anniversary, and
                                        will only adjust for declines in the
                                        initial market price.

       Anti Dilution Provision:         If the Company issues or sells any
                                        common shares at a price less than the
                                        Preferred Shares' Conversion Price, the
                                        Conversion Price will be reduced to
                                        equal the lowest price received by the
                                        Company for such issuance or sale.

                                        The Company may grant or issue any
                                        warrants, rights or options for the
                                        purchase of common shares or any stock
                                        or security convertible into or
                                        exchangeable for common shares (such
                                        warrants, rights or options being called
<PAGE>
                                        "Options" and such convertible or
                                        exchangeable stock or securities being
                                        called "Convertible Securities"). If the
                                        price per share for which common shares
                                        are issuable upon the exercise of such
                                        Options or the exchange of such
                                        Convertible Securities will be less than
                                        the Conversion Price in effect
                                        immediately prior to issuing the Options
                                        or Convertible Securities, the total
                                        maximum number of common shares issuable
                                        upon the exercise of such Options or the
                                        exchange of such Convertible Securities
                                        will be deemed to have been issued.
                                        There will be no adjustment of the
                                        Conversion Price upon the actual
                                        issuance of Common Shares upon the
                                        exercise of Options or exchange of
                                        Convertible Securities. If the price per
                                        share for which common shares are
                                        issueable upon the exercise or the
                                        exchange of Convertible Securities
                                        subsequently changes, the Conversion
                                        Price will be adjusted, but only if the
                                        effect is to reduce the Conversion
                                        Price. On the termination of any Options
                                        or right to exchange or convert
                                        Convertible Securities, the Conversion
                                        Price then in effect will be increased
                                        to the price which would have been in
                                        effect, had such Options or Convertible
                                        Securities, to the extent outstanding
                                        immediately prior to such termination,
                                        never been issued.

                      Mandatory
                    Redemption:         The Preferred Shares will be redeemed in
                                        full at maturity.

                 Voting Rights:         The affirmative vote of the holders of
                                        not less than a majority of the
                                        outstanding Preferred Shares and common
                                        shares is required for the approval of
                                        (i) any merger or consolidation of the
                                        Company with any other corporation; (ii)
                                        any sale, lease, exchange or other
                                        disposition by the Company of all or
                                        substantially all of its assets; (iii)
                                        any increase in the number of authorized
                                        common shares or preferred stock; or
                                        (iv) the dissolution, liquidation or
                                        winding up of the Company. The
                                        affirmative vote of the holders of not
                                        less than a majority of the outstanding
                                        Preferred Shares is required for the
                                        approval of (i) any amendment to the
                                        articles or bylaws of the Company that
<PAGE>
                                        would (a) change the rights, preferences
                                        or privileges of the Preferred Shares or
                                        (b) permit the issuance of new preferred
                                        stock at parity or senior to the
                                        Preferred Shares; or (ii) the making of
                                        any Restricted Payments (as defined in
                                        the indenture governing the Notes (the
                                        "Indenture")) not currently permitted by
                                        the Indenture.

                                        Except as described above or otherwise
                                        required by law, all common shares and
                                        Preferred Share vote together as a
                                        single class on all actions to be taken
                                        by the Company's stockholders. Each
                                        Preferred Share entitles the holder to
                                        such number of votes as will equal the
                                        number of Common Shares into which such
                                        Preferred Share is then convertible.


         Registration: The Company will register the Preferred Shares within 120
days of closing.