OBJECTIVE: To investigate the effects of providing a motorized scooter on physical performance and mobility. DESIGN: Randomized clinical trial comparing scooter users with usual care. SETTING: One academic and 1 Veterans Affairs medical center. PARTICIPANTS: Ambulatory, community-dwelling outpatients with rheumatoid arthritis or osteoarthritis of the knee. INTERVENTION: Provision of a motorized scooter for 3 months. MAIN OUTCOME MEASURES: Six-minute walk distance (6MWD) and mobility methods in diverse locations at baseline, 1 month, and 3 months, and accidents while using the scooter. RESULTS: The majority of scooter subjects (n=16/22 [72.7%]) used the scooter 4 or more days per week. The difference+/-standard deviation between the 2 groups in change in 6MWD over the study period was not statistically significant (scooter users, 16.9+/-73.0 m [55.5+/-239.6 ft]; usual care, 17.2+/-72.5 m [56.5+/-238.0 ft], P=.55). Four (18.1%) scooter users reported 9 accidents. Over the study period, the proportion of persons reporting use of a scooter (provided by the study or otherwise available) increased in the scooter-users group (eg, food stores, 16.7% to 52.6%; doctor's office, 0% to 35.7%) but not the usual-care group (food stores, 9.1% to 9.5%; doctor's office, 0% to 0%). CONCLUSIONS: Motorized scooters provided to ambulatory persons with arthritis were used intermittently. The greatest short-term risk from scooter usage appeared to be minor collisions.