Four hundred ninety-eight long-distance runners aged 50 to 72 years were compared with 365 community control subjects to examine associations of repetitive, long-term physical impact (running) with musculoskeletal disability and medical service utilization in a cross-section study. Runners had less physical disability than age-matched control subjects (p less than 0.01) and maintained more functional capacity (p less than 0.001) as measured by a modified Health Assessment Questionnaire Disability Index. Runners sought medical services less often, but one third of the visits that they did make were for running-related injuries. No differences were found between groups in conditions thought to predispose to osteoarthritis and musculoskeletal disability. Ligamentous laxity and family history of arthritis were similar in both groups. Runners demonstrated better cardiovascular fitness and weighed less. Differences persisted after adjustment for age, occupation, and sex, and after inclusion or exclusion of subjects with major medical problems. Musculoskeletal disability appeared to develop with age at a lower rate in runners (0.003 units per year versus 0.028) than in community control subjects, and the decreased rate was observed with both lower extremity and upper extremity functions. These data suggest positive effects of systematic aerobic running activity upon functional aspects of musculoskeletal aging.