To the Editor: There are many recognized physical risks to the serious runner, ranging from external attacks by birds of prey1 to occult internal bleeding.2 Recent experience with two patients led us to suspect that yet another malady may be associated with serious running: cecal volvulus. Patient 1 was a 160-lb (72-kg) man who was 6 ft 3 1/2 in. (192 cm) tall and 42 years old. He ran 50 miles (80 km) each week. In the previous six years, he had run in 10 marathons, with a best time of 3 hours and 54 seconds. He was in excellent.