Early detection of accelerating frailty in aged primary care patients may help avoid hospitalization, nursing home placement, and loss of self-care. Declines in lower extremity function, and particularly in walking speed, have been shown in prospective cohort studies to correlate strongly with a higher risk of such events. Measurements of walking speed in these studies have been done by specially trained staff in controlled research settings. The effectiveness of routinely measuring walking speed as an indicator of progressing frailty has not been demonstrated in community primary care practices. Objective: To test whether the walking speed of frail aged patients can be obtained reliably and routinely in community primary care practices. Design: (1) A study in community primary care practices of the reliability (reproducibility) of walking speed measurements done by regular patient care staff who are appropriately trained; (2) a study of the feasibility of routinely measuring the walking speed of aged frail patients in this setting by observing the process, determining compliance with protocols, noting the time and effort required for measurements, and by surveying the participants. Settings: Practices of an established rural primary care research network, health clinics in minority neighborhoods, a family practice residency, urban and suburban primary care offices. Main Outcome Measures: (1) the reproducibility of walking speed measurements; (2) feasibility, as determined by percent of eligible patients tested, adherence to protocol, time and effort required, acceptability to patients and staff, and safety. Consequences: If reliability and feasibility of measuring """"""""walking speed as a geriatric vital sign"""""""" is demonstrated, these sites will participate in a subsequent longitudinal study to test the utility of gait speed as a predictor of geriatric patient decline in primary care practices.