Department of Chemistry, Khallikote College (Autonomous), Berhampur-760 001, India E-mail : rspanda50@hotmail.com Manuscript received 25 November 2003, revised 27 May 2004, accepted 16 July 2004 The kinetics of oxidation of cyclic ketones by peroxomonosulfuric acid (PMSA) have been studied in the pH range 0-9.65. The reaction follows second-order kinetics- first-order each in [PMSA] and [ketone] at constant pH. The observed pH-rate profile has been rationalised invoking HSO-5, SO2-5, the protonated and unprotonated forms of cyclic ketone as the reactive species, and their reactivities have been determined. The activation parameters of the reactions have been evaluated. A mechanism consistent with rate-determining nucleophilic attack of peroxo species on carbonyl-carbon of the neutral as well as protonated form of the cyclic ketone molecule has been proposed.