Using specific instruments and scales to measure mental status, nutritional state, visual acuity, gait, and activities of daily living, we studied 79 medical inpatients aged 70 years or older. We then interviewed the patients' primary physicians and nurses and asked them to rate their patients. The prevalence of functional impairment was high: 25 (32%) of the 79 patients were mentally impaired, 31 (39%) were malnourished, 18 (23%) were visually impaired, 31 (39%) had impaired gait, and 23 (29%) had problems with continence. Although clinicians recognized severe impairments, the sensitivity of their clinical judgment was poor in detecting moderate impairment in four categories: mental status sensitivity was 28% (5/18); nutrition, 54% (14/26); vision, 27% (4/15); and continence, 42% (5/12). With clinical judgment alone, physicians and nurses correctly identify severe impairment, but the more prevalent moderate impairments in mental status, nutrition, vision, and continence are poorly recognized. Comprehensive functional assessment instruments can detect these moderate impairments, which may be remediable through early intervention.