Several authors have suggested that the risk of developing aminoglycoside nephrotoxicity is greater in cirrhotic patients than in the noncirrhotic population. However, this has not been confirmed by other investigators. To compare the intensity and characteristics of aminoglycoside nephrotoxicity in cirrhotic and normal rats, 31 rats with carbon tetrachloride-induced cirrhosis with ascites and 35 control rats were treated with gentamicin. Each group of rats was divided into two subgroups in order to receive 10 or 40 mg per kg per day of gentamicin, and different subsets of animals were killed on Days 4, 8 and 12 of treatment for renal histological examination and determination of renal tissue gentamicin concentration. Urine volume, osmolality, sodium excretion and N-acetyl-β-D-glucosaminidase activity were measured daily throughout the study. Creatinine clearance and trough plasma concentration of gentamicin were determined in each animal immediately before killing. There were no significant differences between cirrhotic and control rats in relation to the magnitude of changes in urine volume, osmolality, sodium excretion and N-acetyl-β-D-glucosaminidase activity and creatinine clearance during gentamicin administration. The values of a histopathological score semiquantitatively assessing the renal morphological changes observed by light microscopy were not significantly different in cirrhotic and control rats. In addition, similar trough plasma and renal cortical tissue concentrations of gentamicin were observed in both groups of animals. These results suggest that, in this experimental model, cirrhosis does not increase the risk for aminoglycoside nephrotoxicity.