The induction of the gene RNR3 was investigated in yeast Saccharomyces cerevisiae using RNR3/ lacZ fusion. Gene induction was monitored by measuring β-galactosidase activity. Various drugs that cause DNA damage effectively induced RNR3 expression; alkylating agents (cisplatin, mitomycin C and N-methyl- N′-nitro- N-nitrosoguanidine), a radical producer (bleomycin), and an intercalator (actinomycin D) induced RNR3. When yeast expressing rat CYP1A1 was exposed to 2-aminofluorene, a concentration-dependent induction of RNR3 was observed. Aflatoxin B 1 also induced the expression of RNR3 in the same yeast strain concomitant with inhibition of cell growth. In control yeast, no induction of RNR3 was observed upon exposure to 2-aminofluorene or aflatoxin B 1. Exposure to 2-acetylaminofluorene or benzo[ a]pyrene did not lead to induction of RNR3 in yeast expressing CYP1A1. These results indicate that DNA damage by chemicals related to carcinogenesis induces RNR3, and that activation of these procarcinogens was required for DNA damage-dependent induction of RNR3.