In briefA 20-year-old black male college brief athlete with sickle cell trait developed excruciating calf, thigh, and lower back pain after running 1½miles in very hot, humid conditions. His creatine kinase peaked above 23,000 U/L and urine myoglobin levels were high; the diagnosis was exertional rhabdomyolysis. The patient's condition improved after hospitalization with aggressive rehydration. About 2 weeks later, with aggressive hydration and limitations on distances run without stopping, he returned to full activity. Athletes with known sickle cell trait should take preventive measures to avoid developing exertional rhabdomyolysis.