The induction of sister-chromatid exchanges (SCEs), chromosomal aberrations and polyploids was investigated in cultured Chinese hamster cells treated with pesticides or a related compound positive in microbial reversion assays. The chemicals tested were captan, captafol, 1,2-dibromoethane (EDB), 1,2-dibromo-3-chloropropane (DBCP), 5-nitro-1-naphrhonitrile (NNN), p-dimethylaminobenzenediazo sodium sulfonate (DAPA), 2-hydrazinoethanol (HEH), vamidothion, dichlorovos (DDVP), N-nitroso-ethylenethiourea (N-nitroso-ETU), and 2,4-dinitrophenyl thiocyanate (NBT). A significant and dose-dependent increase in the frequency of SCEs and chromosomal aberrations was observed in the cell cultures treated with captan, captafol, EDB, DBCP, HEH, DDVP, vamidothion, DAPA or N-nitroso-ETU or NBT produced a significant increase in the frequency of polyploid cells, whereas the other agents did not. When compared with results from microbial reversion assays, a close correlation was observed between the ability to induce SCEs or chromosomal aberrations and the mutagenic potency in bacteria (r:0.71-0.84).