In a study of ten young and seven elderly healthy men we have performed an oral glucose tolerance test (75 g) and employed a euglycemic hyperinsulinemic (0.25 mUx kg/min) glucose clamp technique in order to determine insulin sensitivity. This latter experimental protocol consisted of 120 min of euglycemic clamp followed by 60 min in which the clamp and a mild muscular exercise (35% VO(2) (max)) were combined. D-[(3)H]glucose infusion allowed a determination of the glucose turnover parameters. Our results show that in elderly subjects glucose disappearance rate and glucose metabolic clearance rate are significantly lower during both clamp, and clamp + muscular exercise studies. On the contrary, hepatic glucose production was similar under both conditions and was independent of age.