In the study, the effects of relatively high single-dose of Ochratoxin A (OTA) and the antioxidant effects of Melatonin (Mel) and Coenzyme Q(10)) (CoQ(10)) on OTA-induced oxidative damages in rats were investigated. A total of 28 male Sprague-Dawley rats were divided into four groups of 7 rats each: Control, OTA, Mel+OTA and CoQ(10)+OTA groups. Malondialdehyde (MDA) levels in the plasma and glutathione (GSH) levels in whole blood were measured; kidneys (for histological inspection and for apoptosis detection by TUNEL method) and bone marrow samples (for chromosome aberration and mitotic index) were taken. The rats in the OTA group showed limited degeneration of tubular cells. In some tubules karyomegaly, desquamated cells and vacuolization were observed by light microscopy. Mel and CoQ(10) treatment significantly reduced the severity of the lesions. MDA levels of the OTA group were significantly higher than the control, OTA+Mel and OTA+CoQ(10) groups, while GSH levels were significantly lower than the control, OTA+Mel and OTA+CoQ(10) groups. Higher incidences of apoptotic bodies were observed in the kidneys of the OTA group although OTA administration did not significantly change the incidence of apoptotic bodies when compared to the control and antioxidant administrated groups. Although the percentage of the mitotic index was lowest in the OTA group, no statistical difference was found among the groups. Additionally, OTA had no numerical and structural significant effects on chromosomes. It was observed that single-dose OTA administration caused oxidative damages in rat kidney and Mel or CoQ(10) treatment appeared to ameliorate the OTA-induced tissue injuries.