Abstract Rhabdomyolysis with myoglobinuria from nontraumatic causes was the sole identifiable explanation for acute renal failure in 15 patients during a three-year period. Myoglobinuria resulted from myopathies, seizures, prolonged coma, strenuous exercise and viral illness. It was invariably accompanied by a triad of orthotolidin-positive urine, pigmented granular casts in the sediment, and marked elevation of serum creatine phosphokinase levels. In addition, myoglobinuric acute renal failure was often accompanied by an unusually rapid increase in serum levels of creatinine, potassium and inorganic phosphate. Six patients had hypocalcemia (levels of ≤ 7 mg/100 ml) early in the course of acute renal failure; in three of these hypercalcemia developed in the diuretic phase. This hypercalcemia may be unique for myoglobinuric acute renal failure, perhaps as a result of deposition and resorption of calcium phosphate salts in tissues. Nontraumatic myoglobinuria with acute renal failure is a relatively common d...