The aim of our study was to find whether ochratoxin A (OTA) induces the apoptosis and/or necrosis of kidney tissue in rats. In the first experiment, the highest number of apoptotic cells was found in rats sacrificed one day after OTA administration (1.00 mg/kg b.w., i.p.). The number of apoptotic cells reduced gradually and they were not seen nine days after OTA administration. A possible dose-dependence of histological changes was checked in kidney tissue of rats given 0.25, 0.50 or 1.00 mg of OTA/kg b.w., i.p. three times a week for four weeks. The number of apoptotic cells showed a clear dose-dependence, but necrosis was absent even at the highest doses. The time-dependent appearance of lesions related to OTA administration was checked by administering 0.50 mg OTA/kg body weight to rats, and sacrificing them one day after 1, 3, 6, and 9 doses/administrations, or 6 and 21 day after 12 doses/administrations. Long-term administration is associated with continued and increased apoptosis without necrosis, suggestive of OTA's role in the pathogenesis of progressive renal atrophy.