The reactions between edaravone and various one-electron oxidants such as OH, N 3 , Br 2 - , and SO 4 - , have been studied by pulse radiolysis techniques. The transient species produced by the reaction of edaravone with OH radical shows an absorption band with λ max = 320 nm, while the oxidation by N 3 , Br 2 - , SO 4 - and CCl 3OO results in an absorption band with λ max = 345 nm. Different from the previous reports, the main transient species by the reaction of edaravone with OH radical in the absence of O 2 is attributed to OH-adducts. At neutral condition (pH 7), the rate constants of edaravone reacting with OH, N 3 , SO 4 - , CCl 3OO , and e aq - are estimated to be 8.5 × 10 9, 5.8 × 10 9, 6 × 10 8, 5.0 × 10 8 and 2.4 × 10 9 dm 3 mol −1 s −1, respectively. From the pH dependence on the formation of electron adducts and on the rate constant of edaravone with hydrated electron, the p K a of edaravone is estimated to be 6.9 ± 0.1.