A time- and dose-dependent increase in 8-hydroxydeoxyguanosine (8-OHdG) was observed in rat hepatic DNA after a single i.p. injection of aflatoxin B1 (AFB1). It was also found that pre-treatment with selenium or deferoxamine significantly reduced 8-OHdG level in AFB1-administered rats. In contrast, no reduction in 8-OHdG concentration was found in vitamin E-pre-treated rats. These results provide evidence that AFB1 causes oxidative DNA damage in rat liver, which may involve hydroxyl radicals as the initiating species. It is postulated that AFB1-induced oxidative DNA damage (8-OHdG formation) may constitute an important pathway in AFB1 hepatocarcinogenesis.