The effects of dietary protein both before and after uranyl-nitrate-induced acute renal failure were investigated. Male Sprague-Dawley rats were maintained on high-protein (60%), normal-protein (20%), low-protein (5%) and no-protein diets for 8 days prior to intravenous administration of uranyl nitrate (10 mg/kg). Immediately following uranyl nitrate injection, some rats on normal-protein diets were switched to no-protein, low-protein or high-protein diets, while some of the rats on high-protein diets were switched to low-protein diets. Serum and urine creatinine levels and urine volumes were monitored for 2 weeks following uranyl nitrate treatment. Rats conditioned to no-protein and low-protein diets exhibited significantly lower mortalities than rats maintained on normal-protein diets. Rats maintained on high protein diets exhibited better renal function than rats maintained on lower dietary protein regimes, but these rats had mortality rates similar to rats maintained on normal-protein diets. Shifting the rats on normal-protein diets to low- or no-protein diets immediately after uranyl nitrate administration did not improve their renal function or survival rates. However, shifting the rats on normal-protein diets to high-protein diets immediately following uranyl nitrate injection resulted in significantly higher mortalities (93%) than in rats maintained on either normal or high dietary protein throughout the experimental period. Finally, shifting rats on high dietary protein to low-protein diets immediately following uranyl nitrate administration resulted in both improved renal function and survival compared with rats shifted from normal to restricted dietary protein (5%) immediately following uranyl nitrate injection. The above findings indicate that dietary protein prior to as well as following uranyl nitrate administration can have a significant effect on subsequent renal function and survival. Both high and low dietary protein regimes prior to uranyl nitrate administration in rats can significantly improve survival when these animals are maintained on restricted dietary protein following treatment with uranyl nitrate.