Acute renal failure (ARF) is the main cause of death following snake bites by Bothrops species. In this study, we investigated the morphologic and functional renal disturbances caused by Bothrops moojeni venom in rats. Renal function was assessed based on creatinine and lithium clearances and on histologic examination of renal tissue 5 hr after the intravenous administration of 0.2 mg of venom/kg and 5 hr, 16 hr, and 48 hr after 0.4 mg of venom/ kg. A venom dose of 0.4 mg/kg produced renal tubule disturbances, including acute impairment of proximal and post-proximal tubule sodium handling associated with acute tubule necrosis. The glomerular filtration rate (GFR) decreased significantly and was accompanied by severe morphologic disturbances in the renal glomeruli. These functional and morphologic findings were observed in the absence of any change in mean arterial blood pressure. The decrease in GFR was not related to the presence of fibrin deposits in the glomerular capillary loops. These results suggest an early nephrotoxic action of B. moojeni venom involving significant morphologic and functional changes similar to those observed in snakebite-induced ARF in humans.