BACKGROUND: Exertional rhabdomyolysis, although uncommon, is a severe critical illness due to acute renal failure(ARF) and other complications. This study evaluated the clinical, laboratory characteristics of exertional rhabdomyolysis. METHODS: A retrospective study was conducted which examined 26 patients with exertional rhabdomyolysis from Apr. 2000 to Oct. 2001. RESULTS: Fourteen patients(54%) were diagnosed with heat stroke which mostly occurred as a result of a forced march and 12 patients(46%) were diagnosed with exercise-induced rhabdomyolysis which mainly occurred during basic or guerrilla training. All the patients were severely dehydrated and 8 patients(31%) presented with shock. The patients diagnosed with heat stroke were more at risk to shock, seizures, and disseminated intravascular coagulation, than patients who were not diagnosed with heat stroke. Sixteen patients(62%) were diagnosed with ARF(oliguric ARF 9, non-oliguric ARF 7). Seven patients with oliguric ARF received renal replacement therapy. Most patients presented with normal or hypokalemic state in spite of frequent renal failure and metabolic acidosis. Eight patients(31%), mainly diagnosed with heat stoke, were in hypokalemic state and 4 patients(15%) were in hypophosphatemic state. Three patients(20%) died. Of those who survived, three patients suffered from persisting CNS dysfunction. All of them were victims of the heat stroke. CONCLUSION: Acute renal failure was a common complication of exertional rhabdomyolysis. Severe dehydration, shock, and hypokalemia were common during the early course of exertional rhabdomyolysis, especially in patients with heat stroke which was a main, poor prognostic factor of exertional rhabdomyolysis.