Gentamicin, an aminoglycoside antibiotic, is widely used in the treatment of Gram-negative infections; however, dose-limiting nephrotoxicity restricts its optimal use. We investigated the effect of a daily sesame oil supplement on oxidative-stress-associated renal injury induced by a single daily dose of gentamicin in rats. Renal injury was induced by a single subcutaneous daily dose of gentamicin (100 mg kg(-1) d(-1) for 7 days), and then the effects of oral sesame oil (0.25, 0.5, and 1 mL kg(-1) d(-1) for 7 days) on renal injury, oxidative stress, hydroxyl radical, superoxide anion, and NO were assessed after treatment. Sesame oil inhibited gentamicin-induced renal injury, lipid peroxidation, hydroxyl radical, and superoxide anion, as well as NO production. In addition, sesame oil inhibited xanthine oxidase activity and inducible NOS expression in gentamicin-challenged rats. We hypothesize that a daily sesame oil supplement attenuates oxidative-stress-associated renal injury by reducing oxygen free radicals and lipid peroxidation in gentamicin-treated rats.