Thirty patients with drug associated acute nontraumatic rhabdomyolysis were evaluated. Acute renal failure, oliguric (ORF) in ten and nonoliguric (NORF) in another ten patients, was observed. The remaining ten patients did not develop renal failure (NRF). To identify factors that may have contributed to this clinical diversity, these three groups were compared. Data from 51 patients reported in the literature were also included in the analysis. The patients with ORF were slightly younger than patients with NORF. They had higher incidence of muscle swelling and higher serum potassium. ORF was more severe, lasted longer, and required more dialysis than NORF. The group of patients with renal failure had higher incidence of coma and more patients with very high muscle enzyme elevation than NRF patients. Hypercalcemia, a unique complication of rhabdomyolysis, was reported in 22 patients. It was not seen in patients without renal failure. There were no differences in age, incidence of coma, muscle swelling, and muscle enzyme between those who did and those who did not develop hypercalcemia. Sixteen patients with nerve entrapment had higher incidence of coma and muscle swelling than the rest of the patients.