In order to decrease toxicity and/or increase radiosensitizing activity, a new 2-nitroimidazole derivative, methyl 2-nitroimidazole-1-acetohydroxamate (KIN-804), was synthesized to solve the problem of tumor hypoxia. Evaluation of the efficiency of KIN-804 was carried out through studying the antioxidant enzyme system: The superoxide dismutase (SOD), catalase and lipid peroxide levels provide a rough index of the balance between free radical generation and scavenging. Female albino mice were inoculated with Ehrlich ascites carcinoma (EAC) in the thigh. The administration of KIN-804 (i.p. 80 mg/kg body weight) was carried out 20 min before localized irradiation of 10 Gy. In general, the data revealed that KIN-804 administration, followed or not by gamma irradiation, exerted significant inhibition of SOD and catalase activities accompanied by a significant increase in lipid peroxide level in tumor-bearing mice.