there are few studies of ochratoxin a (ota) genotoxicity in experimental animals and the results obtained with cell cultures are inconsistent, although the carcinogenic potential of ota for the kidney of experimental animals has been well established. we studied the genotoxic potential of ota in the kidney of adult female wistar rats (5 in each group) treated intraperitoneally with ota (0.5 mg kg body weight-1 day-1 for 7, 14, and 21 days) measuring dna mobility on agarose gel stained with ethidium-bromide using standard alkaline single-cell gel electrophoresis (comet assay). negative control animals were treated with solvent (tris buffer, 1.0 mg/kg) and positive control animals were treated with methyl methanesulfonate (40 mg/kg) according to the same schedule. ota concentrations in plasma and kidney homogenates in 7-, 14-, and 21-day treated animals were 4.86 ± 0.53, 7.52 ± 3.32, 7.85 ± 2.24 μg/ml, and 0.87 ± 0.09, 0.99 ± 0.06, 1.09 ± 0.15 μg/g, respectively. in all ota-treated groups, the tail length, tail intensity, and tail moment in kidney tissue were significantly higher than in controls (p < 0.05). the tail length and tail moment were higher after 14 days than after 7 days of treatment (p < 0.05), and still higher after 21 days (p < 0.05). the highest tail intensity was observed in animals treated for 21 days, and it differed significantly from animals treated for 7 and 14 days (p < 0.05). ota concentrations in plasma and kidney tissue increased steadily and ota concentration in kidney tissue strongly correlated with tail intensity and tail moment values. these results confirm the genotoxic potential of ota, and show that the severity of dna lesions in kidney correlates with ota concentration.