Body composition was measured in a group of 35 healthy men and 37 healthy women aged 60-83 y. Body mass index (BMI) in men was 25.0 ± 2.2 kg/m2 (i�± SD) and in women, 25.9 ± 3.2 kg/m2. BMI was low in relation to body fat percentage as determined by skinfold-thickness measurements or densitometry in comparison with the relation found in younger adults. Mean body fat percentage ofthe male subjects (aged 70.4 ± 5.2 y) as deter- mined by densitometry was 31.0 ± 4.5%, whereas in women (aged 68.0 ± 5.2 y) it was 43.9 ± 4.3%. Body impedance correlated with fat-free mass (FFM). The best prediction formulas for the FFM from body impedance and anthropometric variables were 1) FFM (kg) = (0.671 x iOx H2/R) + 3.lS + 3.9 where H is body height (m), R is resistance (fl), and S is gender (females, 0; males, 1) (r = 0.94; SEE = 3. 1 kg) and 2) FFM (kg) = (0.360 X l0� x H2/R) + 0.359BW + 4.5S - 20T + 7.0 where BW is body weight(kg)and T is thigh circumference(m) (r = 0.96; SEE = 2.5 kg). The prediction equations from the literature, generally determined in younger populations, overestimated FFM in elderly subjects by �-6 kg and are not applicable to elderly subjects. Am J C/in Nutr l990;5 1:3-6.