February   , 2000

Dear Olsten Stockholder:

    Olsten has agreed to enter into a transaction in which it will merge with a
U.S. subsidiary of Adecco SA and at the same time distribute its health services
businesses to you and all of our other stockholders. Olsten's health services
business is operated by its subsidiary Gentiva Health Services, Inc.

    After the merger, Olsten will be a wholly-owned subsidiary of Adecco and
Gentiva Health Services will be an independent, publicly-owned company.

    In the merger, in exchange for each share of Olsten common stock or class B
common stock you own:

       - Adecco will give you, at your election, either:

           - $8.75 in cash; or

           - 0.12472 of an Adecco American Depositary Share, representing Adecco
             common shares.

       - you will also receive 0.25 of a share of Gentiva Health Services common
         stock.

    To elect the form of consideration you want to receive in the merger, you
must complete the enclosed form of election/letter of transmittal and send it in
with your Olsten stock certificates so that they are received by 4:00 p.m.,
March   , 2000. Even if you do not wish to elect the form of consideration, you
should still send in your stock certificates with the form of election/letter of
transmittal before the merger. Because Adecco will pay cash for half of the
Olsten stock and ADSs for the other half, if stockholders owning more than 50%
of the total outstanding shares of Olsten stock elect cash or elect ADSs, those
stockholders will receive a combination of cash and ADSs for each share of
Olsten stock they own.


    Adecco ADSs are quoted on the Nasdaq National Market under the symbol
"ADECY." Adecco anticipates that its ADSs will be approved for listing on the
New York Stock Exchange and, upon this listing, Adecco ADSs will be dequoted
from the Nasdaq National Market. The shares of common stock of Gentiva Health
Services are anticipated to be approved for quotation on the Nasdaq National
Market under the symbol "GTIV."


    At a special meeting of our stockholders, you will be asked to vote for the
merger and for executive compensation and employee benefit plans of Gentiva
Health Services. A vote for the merger has the effect of also approving the
split-off since part of the consideration for the merger is the shares of
Gentiva Health Services common stock. If the merger is not consummated, the
split-off of Gentiva Health Services from Olsten will not occur. No separate
vote on the split-off is required or is being requested. The approval of the
merger is not conditioned on the approval of any of the other proposals. The
approval of the executive compensation and employee benefit plans is conditioned
on approval of the merger.

    The holders of a majority of the voting power of Olsten's outstanding common
stock and class B common stock, voting together as a single class, must vote in
favor of the merger and the other proposals for them to be approved. You will be
entitled to one vote for each share of common stock you own and ten votes for
each share of class B common stock you own. Class B common stockholders owning
shares representing 63% of the voting power of Olsten stock as of January 18,
2000 have agreed with Adecco to vote for the merger. Assuming these stockholders
vote their stock at the special meeting as they have agreed, the necessary vote
for approving the merger will be assured.

    OLSTEN'S BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE FOR THE
MERGER.

    The accompanying proxy statement/prospectus provides detailed information
about the meeting and the proposed merger. The Gentiva Health Services
prospectus attached as Annex A describes Gentiva Health Services' business,
management and financial condition. Olsten's board encourages you to read the
entire proxy statement/prospectus and all of attached annexes carefully.


                                    
/s/ Edward A. Blechschmidt             /s/ Stuart Olsten
  President and Chief Executive          Chairman of the Board
  Officer                                Olsten Corporation
  Olsten Corporation