Myoglobinuric renal failure occurred in association with influenza A2 (London) upper respiratory infection in a previously healthy 21-year-old man. The usual influenza symptoms of nonproductive cough, sore throat, nausea, mild diarrhea, and myalgia progressed to dehydration and concomitant tender muscles and myoglobinuria. Thrombocytopenia was also noted. The influenza symptoms, thrombocytopenia, and myoglobinuric renal failure resolved spontaneously; however, the patient required brief supportive peritoneal dialysis before recovery was complete. Tender muscles in patients with upper respiratory-tract illness should alert physicians to this syndrome.