To examine the effect of resistance training (RT) on insulin sensitivity we studied 13 previously sedentary non-obese non-insulin dependent diabetics (NIDDM) before and after 4-6 weeks of either RT (n=8) or no exercise (sedentary controls, n=5). The training program consisted of 2 sets of the following 9 exercises with 10-20 repetitions: arm curl, military press, push ups, squat, knee extension, heel raise, back extension, bent knee extension and upright rowing. Subjects trained 5 times a week. Glycosylated hemoglobin, insulin sensitivity assessed by euglycemic hyperinsulinemic clamp, body composition by dualenergy X-ray absorptiometry and maximal oxygen uptake (VO2max) were measured before and after the training period in both groups. The two groups did not differ significantly on any variables before the programs. Glucose disposal rates (GDR) during the euglycemic hyperinsulinemic clamp increased 47% in the RT group (6.69±1.92 to 9.84±3.24 mg/kg lean body mass/min, p<0.005) and did not change in the sedentary controls (6.38±1.97 to 6.83 ± 1.92 mg/kg lean body mass/min). Glycosylated hemoglobin improved significantly in a similar manner in both groups. There was no significant change in VO2max in the RT group. It was concluded that RT improved insulin sensitivity in non-obese NIDDM without any changes in VO2max.