The oxidation of 3-hydroxyflavone (flaH) to O-benzoylsalicylic acid (O-bsH) initiated by 2,2-diphenyl-1-picrythydrazyl (DPPH) has been investigated in acetonitrile at ambient temperature. The kinetics was followed by monitoring the disappearance of DPPH spectrophotometrically at 520 nm and the rate constants were determined according to the rate law -d[DPPH]/dt = k [DPPH] [Substrate]. The mean value of the rate constant k at 295 K is 1.21 +/- 0.03 dm(3) mol(-1) s(-1).