DNA damage detected by the comet assay (single cell gel electrophoresis) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation in DNA in the bone marrow has been studied in groups of 6 male Wistar rats treated with a single i.p. injection of the carcinogen 2-nitropropane (2-NP, 100 mg/kg body weight) or vehicle. Twenty-four hours after 2-NP the average tail length in the comet assay in bone marrow cells was increased from 1.46 +/- 0.27 to 9.61 +/- 1.56 microm (mean /- SD, p < 0.01), and 8-oxodG levels in the DNA were increased from 1.04 +/- 0.50 to 5.14 +/- 2.42 per 10(5) dG (p < 0.01). There was a close correlation between the comet tail length and the 8-oxodG level (r = 0.89, p < 0.05). The results indicate that 2-NP inflicts DNA damage in the bone marrow cells and thus could be leukemogenic.