The repair activities and mechanisms of both quercetin and rutin towards the oxidizing deoxyguanosine monophosphate (dGMP) hydroxyl radical adduct were investigated with pulse radiolytic technique. On pulse irradiation of nitrous oxide saturated 2mM dGMP aqueous solution containing 0.1mM quercetin, the transient absorption spectrum of the dGMP hydroxyl radical adduct decays with the formation of phenoxyl radical of quercetin within tens of microseconds. It indicates that there is a repair reaction between dGMP hydroxyl radical adduct and quercetin. The repair activity of rutin towards hydroxyl radical adducts of dGMP was also observed. The rate constants of the repair reactions were calculated to be 3.05x10 8 and 1.31x10 8 M - 1 s - 1 for quercetin and rutin, respectively. This result together with our previous studies demonstrated that non-enzymatic, fast repair is a universal repair mechanism of phenolic antioxidants.