Chemistry Department, Govt. Science College, Rewa-486 001 Manuscript received 1 March 1983, revised 20 January 1984, accepted 3 May 1984 The kinetics of oxidation of acetyl acetone in 50% (v/v) acetic acid-water by selenium dioxide has been studied. The reaction follows first order kinetics with respect to both selenium dioxide and acetyl acetone. The effects of sulphuric acid, neutral salts, solvent polarity and temperature on the rate of oxidation have been studied. The energy of activation, frequency factor, entropy of activation and free energy of activation have values 15.56±0.6 kcal mol-1, 4.29±0.3x 106 dm3 mol-1sec-1, -27.9±1.0 e.u. and 24.96±0.8 kcal mol-1, respectively. A mechanism of oxidation, consistent with experimental observations has been proposed.