In this study, we aimed to evaluate the effect of vitamins A, C, and E against aflatoxin B, (AFB(1)) on blood cultures in relation to induction of sister chromatid exchange (SCE). The results indicated genotoxic and mutagenic damage in cultured human lymphocytes exposed to AFB(1). The results showed that 5 mu M concentration of AFB(1) increased SCE. When vitamins A, C and E were added to AFB(1), the frequency of SCE decreased. These results suggest that vitamins A, C, and E could effectively inhibit AFB(1)-induced SCE, which may partially responsible for its mutagenic effect of AFB(1). Besides, the protective effect of vitamins A, C, and E against AFB(1) was increased in a dose-dependent manner (i.e., as the doses increased, their protective effects also increased). There was a significant decrease in the SCE frequency in AFB(1)-treated group compared with the groups receiving AFB(1) and also vitamins A, C, and E. The most effective concentration was 100 microM vitamin C, and the lowest effective concentration was 0.5 microM vitamin A. Vitamin C has the most effective concentration of 100 mu M, and vitamin A has the lowest effective concentration of 0.5 mu M. The order of the decreasing effect of the SCE frequency of vitamins was as follows: vitamin C > vitamin E > vitamin A. Toxicology and Industrial Health 2009; 25: 183-188.