Post-Graduate Department of Studies in Chemistry, Karnatak University, Dharwad-580 003, India E-mail : karuni@bgl. vsnl.net. in Manuscript received 12 June 2001, revised 3 October 2002, accepted 22 November 2002 The kinetics of oxidation of DL-methionine by cerium(IV) in aqueous perchloric acid solution have been studied spectrophotomctrically. The reaction shows first order kinetics in [CeIV] and an apparent less than unit order dependence each in [DL-methionine] and [acid]. The data suggest that the oxidation proceeds via the formation of a complex between methionine and cerium(IV) which decomposes in a slow step to give a free radical which on reacting with one more molecule of cerium(IV) in a fast step gives the products. The reaction constants involved in the mechanism are evaluated.