Objective To identify a standard physical performance test, which can predict 3-year incident mobility disability independent of demographics. Design Longitudinal cohort study. Setting Population-based middle-aged and older adult cohort assessment performed at a local geriatric clinical center. Participants Community-living middle-aged and older persons (age, 50–85y) without baseline mobility disability (N=622). Interventions Not applicable. Main Outcome Measures Mobility disability was ascertained at baseline and at 3-year follow-up using an established self-report method: self-reported inability to walk a quarter mile without resting or inability to walk up a flight of stairs unsupported. Physical performance tests included self-selected usual gait speed, time required to complete 5 times sit-to-stand (5TSTS), and 400-m brisk walking. Demographic variables age, sex, height, and weight were recorded. Results Overall, 13.5% participants reported 3-year incident mobility disability. Usual gait speed <1.2m/s, requiring >13.6 seconds to complete 5TSTS, and completing 400m at <1.19m/s walking speed were highly predictive of future mobility disability independent of demographics. Conclusions Inability to complete 5TSTS in <13.7 seconds can be a clinically convenient guideline for monitoring and for further assessment of middle-aged and older persons, in order to prevent or delay future mobility disability.