OBJECTIVES: To determine whether benzodiazepine use is associated with incident disability in mobility and activities of daily living (ADLs) in older individuals. DESIGN: A prospective cohort study. SETTING: Four sites of the Established Populations for Epidemiologic Studies of the Elderly. PARTICIPANTS: This study included 9,093 subjects (aged ≥65) who were not disabled in mobility or ADLs at baseline. MEASUREMENTS: Mobility disability was defined as inability to walk half a mile or climb one flight of stairs. ADL disability was defined as inability to perform one or more basic ADLs (bathing, eating, dressing, transferring from a bed to a chair, using the toilet, or walking across a small room). Trained interviewers assessed outcomes annually. RESULTS: At baseline, 5.5% of subjects reported benzodiazepine use. In multivariable models, benzodiazepine users were 1.23 times as likely as nonusers (95% confidence interval (CI)=1.09-1.39) to develop mobility disability and 1.28 times as likely (95% CI=1.09-1.52) to develop ADL disability. Risk for incident mobility was increased with short- (hazard ratio (HR)=1.27, 95% CI=1.08-1.50) and long-acting benzodiazepines (HR=1.20, 95% CI=1.03-1.39) and no use. Risk for ADL disability was greater with short- (HR=1.58, 95% CI=1.25-2.01) but not long-acting (HR=1.11, 95% CI=0.89-1.39) agents than for no use. CONCLUSION: Older adults taking benzodiazepines have a greater risk for incident mobility and ADL disability. Use of short-acting agents does not appear to confer any safety benefits over long-acting agents.