Melatonin ( MEL) and coenzyme Q10 ( CoQ10) both display antioxidant and free radical scavenger properties. In the present study, the effect of MEL and CoQ10 on the oxidative stress and fibrosis induced by ochratoxin A ( OTA) administration in rats was investigated. Rats were divided into five equal groups, each consisting of seven rats: ( 1) controls; ( 2) OTA- treated rats ( 289 mu g/ kg/ day); ( 3) OTA+ MEL - treated rats ( 289 mu g/ kg/ day OTA+ 10 mg/ kg/ day MEL); and ( 4) OTA+ CoQ10 - treated rats ( 289 mu g/ kg/ day OTA+ 1 mg/ 100 g/ day body weight ( bw) CoQ(10)). After 4 weeks of treatment, the level of malondialdehyde( MDA), glutathione peroxidase ( GPx), and hydroxyproline ( Hyp) were measured in the homogenates of liver and kidney. In the OTA- treated group, the levels of MDA and Hyp in both liver and kidney were significantly increased when compared with the levels of control, whereas GPx activities decreased. InOTA+ MEL - treated rats, the levels of MDA and Hyp in both liver and kidney were significantly decreased when compared with the levels of OTA- treated rats; however; GPX activities increased. In the OTA+ CoQ(10) - treated group, the levels ofMDA and Hyp were decreased when compared with the levels ofOTA- treated rats, whereas GPx activities increased. In theOTA+ CoQ(10) - treated group, the levels of MDA, Hyp, and GPx were not significantly changed in kidney when compared with OTA- treated group. MEL has a protective effect against OTA toxicity through an inhibition of the oxidative damage and fibrosis both liver and kidney. Although CoQ(10) has protective effect against OTA toxicity in liver tissue, it has no effect in kidney tissue.