The effects of intramuscular glycerol on ischemic acute renal failure was investigated in dogs. Anesthetized dogs received a bilateral 120-min renal artery obstruction (RAO) alone, RAO plus 5 ml/kg of 50% glycerol or RAO plus 5 ml/kg of 75% glycerol. Control groups received the glycerol injection, but not RAO. Renal histopathology was minimal in dogs receiving glycerol alone. In RAO dogs, those receiving 50% glycerol showed diffuse acute tubular necrosis (ATN), while those receiving 75% glycerol had severe ATN with extreme mortality. Changes in serum creatinine, creatinine clearance, and fractional excretion of sodium were consistent with the histopathologic changes. We conclude that myoglobinuria, of a degree insufficient to cause renal failure itself, can interact with renal ischemia to significantly exacerbate the renal damage produced.