The effects of dietary restriction (DR) on the activities of liver superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and the level of lipid peroxidation (LP) in developing mice were investigated in this study. Male and female Kunmin mice were fed a standard rodent diet ad libitum (AL); 80% of AL food intake (20% DR) or 65% of AL food intake (35% DR) for 12 or 24 wk. Both 12- and 24-wk of DR resulted in retarded body weight gain in male and female mice. The activities of SOD, CAT and GPx and content of LP in DR male and female mice were not different (P>0.05) from those in controls after 12 wk of DR. However, the SOD activity was increased at 24 wk in 20% DR (P<0.05) and 35% DR (P<0.01) male, but not in DR female mice. The CAT activity was elevated at 24 wk in both DR male (P<0.05 for 20% DR, P<0.01 for 35% DR) and female (P<0.01) mice with a greater increase in DR female (P<0.05) than in DR male animals. GPx activity was also increased at 24 wk in DR male (P<0.01) and female (P<0.01) mice with a greater elevation in DR female (P<0.05) than in DR males. Further, LP was decreased at 24 wk in both DR male (P<0.01) and female (P<0.01) animals with a greater reduction in DR females (P<0.01) compared to DR males. These findings indicated that 24-wk, but not 12-wk, of DR led to differential effects on liver SOD, CAT and GPx activity and LP content in male and female mice during development, suggesting sex-associated modulations of DR on antioxidant systems in developing animals.