Six healthy young subjects (aged 23–32 years), six healthy elderly subjects (over 60 years) and six hospitalized long-stay geriatric subjects over 60 years received single oral doses of acetanilide. Acetanilide clearance was similar in the fit and frail elderly subjects at 26.4 ± 2.5 and 26.3 ± 3.6 1/h and significantly lower (p<0.05) than in the young subjects at 39.0 ± 1.9 1/h. Liver volumes, measured by ultrasound, were significantly less in the elderly than in the young subjects, whether expressed in absolute terms or per unit body weight (p < 0.05). When acetanilide clearance was expressed per unit volume of liver, no change occurred with age or frailty. These results suggest that a reduced liver size may be an important contributor to the reduced elimination of capacity limited drugs in elderly man.