MFS(R) INSTITUTIONAL TRUST:

                   MFS Institutional International Equity Fund
                     MFS Institutional Large Cap Value Fund

                        Supplement to Current Prospectus:


Effective  June 1, 2008, the first two  paragraphs of the  sub-section  entitled
"How to Redeem  Shares"  under the main heading "How to  Purchase,  Redeem,  and
Exchange Shares" are restated in their entirety as follows:


How to Redeem Shares

Your shares will be sold at the net asset value per share next calculated  after
your  redemption  order is received in proper form.  MFSC  reserves the right to
reject  any  redemption  request  that  is  not in  proper  form.  The  specific
requirements  for proper form depend on the type of account and  transaction and
the method of redemption.  A redemption order in an amount less than or equal to
the value of your account (other than an exchange) is considered to be in proper
form only with  respect to shares in your  account  for which  payment  has been
received and collected.  A new redemption order must be submitted if you wish to
redeem  shares for which payment had not been received and collected at the time
the prior  redemption  order was received by the fund.  Receiving and collecting
payment  can take up to seven days after a purchase.  In certain  circumstances,
you  may  need  to have  your  signature  guaranteed  and/or  submit  additional
documentation  to redeem your  shares.  In general,  no  signature  guarantee is
required if redemption proceeds are wired to a predesignated bank account.

Each fund  sends out your  redemption  proceeds  within  seven  days  after your
request is received in proper form.  Under unusual  circumstances,  such as when
the New York Stock Exchange is closed, trading on the Exchange is restricted, or
as permitted by the SEC, each fund may suspend redemptions or postpone payment.

Effective June 1, 2008, the bulleted  sections under the  sub-heading  "Frequent
Trading"  up to,  but not  including  "Frequent  Trading  Risks"  under the main
heading "How to Purchase, Redeem, and Exchange Shares" are restated as follows:

Frequent Trading

     o    Right to Reject or Restrict Purchase and Exchange Orders. The Board of
          Trustees  of the MFS funds  has  adopted  the  purchase  and  exchange
          limitation  policies described below, which it believes are reasonably
          designed to discourage frequent fund share transactions. MFSC seeks to
          monitor and enforce these policies,  subject to oversight by the Board
          of  Trustees.  The MFS  funds  may alter  their  policies  at any time
          without notice to shareholders.

     o    General  Purchase  and  Exchange  Limitation  Policies.  The MFS funds
          reserve the right to restrict,  reject,  or cancel,  without any prior
          notice,  any  purchase  or  exchange  order,   including  transactions
          believed to represent frequent trading activity. For example, MFSC may
          in its discretion  restrict,  reject, or cancel a purchase or exchange
          order even if the  transaction is not subject to specific  exchange or
          other limitations described in this prospectus if MFSC determines that
          accepting the order could interfere with the efficient management of a
          fund's  portfolio,  increase costs to the fund, dilute the value of an
          investment in the fund to long-term shareholders,  or otherwise not be
          in the  fund's  best  interests.  In the event  that MFSC  rejects  or
          cancels an exchange  request,  neither the redemption nor the purchase
          side of the exchange  will be  processed.  Each MFS fund  reserves the
          right  to  delay  for one  business  day the  processing  of  exchange
          requests in the event that, in MFSC's judgment, such delay would be in
          the  fund's  best  interest,  in which  case both the  redemption  and
          purchase side of the exchange will receive the fund's net asset values
          at the conclusion of the delay period.

     o    Financial   Intermediary  Purchase  and  Exchange  Limitations.   MFSC
          receives  purchase,  exchange and redemption  orders through financial
          intermediaries. A financial intermediary's policy restricting frequent

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          trading may be more or less  restrictive than the MFS funds' policies,
          may  permit  certain  transactions  not  permitted  by the MFS  funds'
          policies,  or  prohibit  transactions  not  subject  to the MFS funds'
          policies. You should consult your financial intermediary regarding the
          application   of  these   limitations   and  whether  your   financial
          intermediary imposes any additional or different limitations.

     o    Omnibus Accounts.  MFSC receives  purchase,  exchange,  and redemption
          orders  through  certain  financial  intermediaries  that hold omnibus
          accounts with an MFS fund.  Omnibus  account  arrangements  are common
          forms of  holding  shares of MFS  funds,  particularly  among  certain
          financial  intermediaries  such as brokers,  retirement and 529 plans,
          investment  advisors,   and  variable  insurance  products.   MFSC  is
          generally  not able to  identify  trading by a  particular  underlying
          shareholder  within an omnibus  account,  which makes it  difficult or
          impossible  to  determine if a particular  underlying  shareholder  is
          engaged in frequent trading.

          For  omnibus  accounts  for  which  MFSC  does not  regularly  receive
          underlying  shareholder  data,  MFSC reviews  trading  activity at the
          omnibus level to detect suspicious  trading  activity.  This review is
          based on MFSC's internal  parameters for detecting  frequent  trading,
          including  reviewing  transactions that exceed a certain dollar amount
          or transactions that occur close in time to other  transactions in the
          same account or in multiple  accounts that are under common  ownership
          or influence.  These  parameters may change from time to time. If MFSC
          detects  suspicious  trading  activity  at the  omnibus  level it will
          contact the financial  intermediary to request underlying  shareholder
          level  activity to determine  whether there is underlying  shareholder
          level frequent trading.  If frequent trading is identified,  MFSC will
          take  appropriate  action,  such as  prohibiting  purchases  into  the
          account,  requiring  purchases by mail, or prohibiting  purchases from
          the financial intermediary.

     o    Limitations  on the  Ability to Detect and  Curtail  Frequent  Trading
          Practices.  Depending  upon the  composition  of a fund's  shareholder
          accounts and the efforts made by certain  shareholders  to evade these
          limitations,  MFSC  may not be in a  position  to  monitor  and  deter
          frequent trading with respect to a significant  percentage of a fund's
          shareholders.  MFSC's ability to monitor and deter frequent trading in
          omnibus accounts  ultimately depends on the capability and cooperation
          of the  financial  intermediary  and the  frequency  with  which  MFSC
          requests  underlying  shareholder  account data from omnibus accounts.
          MFSC  expects  to request  underlying  shareholder  account  data less
          frequently  from  financial  intermediaries  who have adopted a policy
          restricting  frequent  trading that MFSC has  determined is reasonably
          designed to identify and curtail  trading  activity that is not in the
          best interest of the funds than from other  financial  intermediaries.
          In  certain  instances,  a  financial  intermediary  may be  unable to
          provide  MFSC with  information  about  underlying  shareholder  level
          activity.  There is no  assurance  that  MFSC will  request  data with
          sufficient  frequency to detect or deter  frequent  trading in omnibus
          accounts  effectively.  Shareholders  seeking  to engage  in  frequent
          trading  practices  may  deploy  a  variety  of  strategies  to  avoid
          detection,  and,  despite  the  efforts  of MFSC to  prevent  frequent
          trading, there is no assurance that MFSC will be able to identify such
          shareholders or curtail their trading practices.


                  The date of this supplement is June 1, 2008.