The present study aimed to investigate the role of silymarin as an antioxidant and/or it activity in induction of the endogenous antioxidants in intact adult male rats. Seventy males were randomly devided into control and silymarin treated groups (35 each), and were drenched with drinking water and silymarin suspension (200 mg/ kg b.w) daily for 40 days. Each group was allocated to 5 equal subgroups; sacrificed before treatment (0 day), and after 10, 20, 30, and 40 days of treatment. At the end of each period, males were anaesthesized, dissected and blood samples were obtained for assessment of MDA, SOD, CAT and GSH concentrations. liver samples (1 g) have been removed and homogenized for assessment of liver subcellular MDA, SOD, CAT and GSH concentrations. At the end of each periods, serum and liver subcellular MAD concentrations showed no significant changes between groups, whereas SOD, CAT, and GSH concentrations significantly increased at 10, 20, 30, and 40 day periods in silymarin treated males compared with control. It can be concluded that silymarin antioxidant activity is of pharmacological value not only as an antioxidant by itself but also as an inducer of endogenous enzymatic and non-enzymatic antioxidants even in normal intact male.