The pathogenesis of gentamicin (GM) nephrotoxicity has been shown to involve the generation of oxygen free radicals, and several free radical scavengers have been shown to ameliorate the nephrotoxicity. The seeds and oil of Nigella sativa are reported to possess strong antioxidant properties and was effective against disease and chemically-induced hepatotoxicity and nephrotoxicity. Therefore, in the present work, we have tested whether oral treatment of rats with N. sativa oil (0.5, 1.0 or 2.0 ml/kg/day for 10 days) would ameliorate nephrotoxicity of GM (80 mg/kg/day given intramuscularly and concomitantly with the oil during the last 6 days of treatment). Nephrotoxicity was evaluated histopathologically with a light microscope and by measurement of concentrations of urea, creatinine and total antioxidant status (TAS) in plasma and reduced glutathione (GSH) and TAS in kidney cortex. The results indicated that GM treatment caused moderate proximal tubular damage, significantly increased the concentrations of creatinine and urea, and decreased that of TAS and GSH. Treatment with N. sativa oil produced a dose-dependent amelioration of the biochemical and histological indices of GM nephrotoxicity that was statistically significant at the two higher doses used. Compared to controls, treatments of rats with N. sativa did not cause any overt toxicity, and it increased GSH and TAS concentrations in renal cortex and enhanced growth. The results suggest that N. sativa may be useful in ameliorating signs of GM nephrotoxicity in rats, and pending further experimentation to determine safety and efficacy, may be useful clinically.