The hyperinsulinemic, euglycemic clamp technique was used to test the hypothesis that--when expressed per kilogram of lean body mass--there is a sex-difference in peripheral insulin-mediated glucose disposal (M), as proposed in the literature. Lean body mass was assessed with tetrapolar bioelectric impedance analysis. We studied 15 normal subjects (volunteers with normal glucose tolerance and body mass indices between 20-25 kg/m2) of both sexes, 9 women and 6 men, of 2 age-groups, 20-30 year-old and 40-50 year-old. Men and women were similarly aged (33.3 +/- 3.8 and 33.3 +/- 3.8 years, respectively). Body mass indices were similar in both sexes (22.5 +/- 0.6 in women and 23.6 +/- 0.7 in men, NS) but percentages of fat mass were not (29.4 +/- 1.2 in women and 20.6 +/- 1.6 in men, p less than 0.001). As no difference in M (mg of glucose metabolized per kilogram of body weight per minute) between age-groups was found (6.4 +/- 0.8 and 6.8 +/- 1.2 mg/kg/min, NS) the data from these 2 age-groups were pooled. When M values obtained in both sexes were compared no differences were found (7.1 +/- 1.5 mg/kg/min in women and 6.3 +/- 0.6 in men, NS). Similarly, when M was expressed in function of the prevailing insulin levels attained during steady-state, M/l, no differences were disclosed (8.98 +/- 2 mg/kg/min/microIU insulin in women and 7.8 +/- 1.2 in men, NS).(ABSTRACT TRUNCATED AT 250 WORDS)