['To examine the association between physical activity and the risk of incident disability, including impairment in activities of daily living (ADLs) and instrumental activities of daily living (IADLs), in community-based older persons free of dementia.', 'Prospective, observational cohort study.', 'Approximately 40 retirement communities across the Chicago metropolitan area.', 'More than 1,000 older persons from the Rush Memory and Aging Project, an ongoing longitudinal clinical-pathological study of common chronic conditions of old age.', 'All participants underwent detailed annual clinical evaluations that included assessments of physical activity, ADLs, IADLs, and gait performance. The associations between physical activity, mortality, and incident disability were examined using a series of Cox proportional hazards models controlled for age, sex, education, and baseline gait.', 'At baseline, participants spent a mean+/-standard deviation of 3.0+/-3.5 hours per week engaging in physical activity (range 0-35). In a proportional hazards model, the risk of death decreased 11% (hazard ratio (HR)=0.89, 95% confidence interval (CI)=0.83-0.95) for each additional hour of physical activity per week. For those who were not disabled at baseline, the risk of developing disability in ADLs decreased 7% (HR=0.93, 95% CI=0.88-0.98) for each additional hour of physical activity per week. Similarly, the risk of disability in IADLs decreased 7% (HR=0.93, 95% CI=0.89-0.99) for each additional hour of physical activity.'] Is physical activity associated with incident disability in community-based older persons?