Three cases of rhabdomyolysis, two with acute renal failure, seen in a short period of time in an emergency department illustrate this increasingly recognized entity. Myoglobinuria may result from muscle trauma, ischemia, metabolic causes, drug-induced injury or intrinsic muscle disorders. The diagnosis is easily made by the presence of an elevated creatine phosphokinase, positive orthotoluidine in the urine and pigmented urine casts. Failure to diagnose rhabdomyolysis early will result in increased morbility and mortality from subsequent hyperkalemia, acute renal failure and hypocalcemia. These three cases illustrate the difficulty in predicting the eventual degree of renal failure from the initial assessment.