Little information is available regarding the long-term effects, if any, of running on the musculoskeletal system. We therefore compared the prevalence of degenerative joint disease among 17 male runners (mean age, 56 years; height, 180 cm [5 ft 11 in]; and weight, 73.02 kg [161 lb] with 18 male nonrunners (mean age, 60 years; height, 178 cm [5 ft 10 in]; and weight, 78 kg [171 lb]). Running subjects (53% marathoners) ran a mean of 44.8 km (28 miles)/wk for 12 years. Pain and swelling of hips, knees, ankles, and feet and other musculoskeletal complaints among runners were comparable with those among nonrunners. Radiologic examinations (for osteophytes, cartilage thickness, and grade of degeneration) also were without notable differences among groups. We did not find an increased prevalence of osteoarthritis among the runners. Our observations suggest, within the limits of our study, that long-duration, high-mileage running need not be associated with premature degenerative joint disease in the lower extremities.