The objective of this study was to examine the effects of antioxidant vitamins on the cellular oxidant damage by observing the mitogenicity in the mouse spleen and the strand breaks of DNA in mouse blood induced by AFB₁. Intraperitoneal(i.p.) injections of vitamin C(VC) of 10 mg/kg and vitamin E(VE) of 63.8 mg/kg were repeatedly administered to male ICR mice of 6 weeks old at intervals of 4 times every 2 days. After one hour vitamin treatments, AFB₁ of 0.4 mg/kg was injected into the AFB₁ plus vitamin treated groups in the same way. On the other hands, into the AFB₁ only treated group, only AFB₁ was injected without vitamins in the same method as above. The results of the experiment are as follows ; as regard to comet assay, DNA strand breaks were clearly present and they formatted a typical comet tail in the mice blood of the AFB₁ only treated groups. However, comet tails apparently disappeared in AFB₁ plus antioxidant vitamins treated groups since oxidant damage was controlled in an almost similar level to the control group. Mitogenicity of the spleen also showed a similar tendency as before, and these differences were more remarkably observed in the reaction against Con-A, which is a T-cell mitogen. In these data, the statistical significance was p<0.01. The LDL and VLDL levels were 408.72, 504.47 mg/dl respectively in the AFB₁ only treated groups. Compared with the AFB₁ only treated groups, those of AFB₁ plus antioxidant vitamin treated groups decreased to 272.06(VC), 305.28 mg/dl(VE), respectively. On the other hand, HDL levels were diminished to 32.60, 29.60 mg/dl in AFB₁ only treated groups, compared to 42.23, 41.14 mg/dl in the AFB₁ plus antioxidant vitamins treated groups. But, blood glucose levels were not statistically significant.