The ability of acrylonitrile to induce cytotoxicity, sister-chromatid exchanges and DNA single-strand breaks was studied in cultured human bronchial epithelial cells. The toxic effect as determined by cloning efficiency was observed at a dose of 600 micrograms/ml but not at doses of both 150 and 300 micrograms/ml. The frequency of sister-chromatid exchange in untreated cells was 3.7 +/- 1.3 per cell. In contrast, cells treated with acrylonitrile at 150 and 300 micrograms/ml exhibited 6.6 +/- 1.3 and 10.7 +/- 1.7 sister-chromatid exchanges per metaphase, respectively. DNA single-strand breaks were induced by acrylonitrile at dose levels of 200 and 500 micrograms/ml. The genotoxic effects on human bronchial epithelial cells that were directly exposed to acrylonitrile are of interest in relation to evidence for the higher lung cancer incidence of acrylonitrile workers in epidemiological studies.