Study objective: To describe the syndrome of exercise-induced rhabdomyolysis and to investigate the relation between exercise-induced rhabdomyolysis and the development of acute renal failure. Design: Retrospective chart analysis on all patients with a discharge diagnosis of rhabdomyolysis from January 1988 to January 1993. Setting: An urban tertiary care center with 225,000 annual emergency department visits. Type of participants: Thirty-five patients met the inclusion criteria for exercise-induced rhabdomyolysis: a history of strenuous exercise, creatine phosphokinase level more than 500, and urine dipstick positive for blood without hematuria. We excluded patients with a history of trauma, myocardial infarction, stroke, or documented sepsis. Charts also were examined for the presence of nephrotoxic cofactors (ie, hypovolemia and/or acidosis). Results: All 35 patients were men without significant past medical history and were an average age of 24.4 years. The average admission creatine phosphokinase was 40,471 U/L. No patient presented with or developed nephrotoxic cofactors during hospitalization. None of our study patients experienced acute renal failure. Conclusion: Previous literature has described a 17% to 40% incidence of acute renal failure in rhabdomyolysis. None of our patients developed acute renal failure, signifying a much lower incidence of acute renal failure in exercise-induced rhabdomyolysis without nephrotoxic cofactors than in other forms of rhabdomyolysis.