TORONTO, ONTARIO -- (MARKET WIRE) -- 09/08/06 -- ValueAct Capital Master Fund, L.P. and ValueAct Capital Master Fund III, L.P. (together, "ValueAct Capital") announce that they acquired an aggregate of 1,787,000 common shares of MDS Inc., comprising approximately 1.2% of the outstanding common shares of MDS Inc., and that following such acquisition they collectively owned 14,674,700 common shares of MDS Inc., comprising approximately 10.2% of the outstanding common shares of MDS Inc. ValueAct Capital acquired the Shares via open market purchases on the Toronto Stock Exchange for investment purposes in the ordinary course of their business and they may, alone, together or together with other joint actors, further purchase, hold, vote, trade, dispose of or otherwise deal in the common shares of MDS Inc. at times, and in such manner, as they deem advisable.

A report containing additional information in respect to the foregoing may be obtained by calling Briana Curran at (415) 249-1205.

Contacts:
ValueAct Capital Master Fund, L.P.
Briana Curran
(415) 249-1205