Aerobic endurance exercise has traditionally been advocated in the treatment of non-insulin-dependent diabetes mellitus (NIDDM). However, the effect of aerobic endurance exercise programs on long-term glycaemic control is small to moderate. The aim of the present study was to determine the effect of circuit resistance training on long-term glycaemic control (HbA1c) and to examine the potential association between muscle size and glycaemic control in NIDDM subjects. Eight NIDDM subjects participated in a 3 month individualized progressive resistance training program (moderate intensity, high-volume) twice a week with measurements of HbA1c, lipids, blood pressure, VO2max and thigh muscle cross-sectional area. There was a significant improvement in HbA1c (8.8% - 8.2%; p < 0.05). Muscle endurance increased by 32 +/- 23% (p < 0.05), and the cross-sectional area of m. vastus lateralis increased by 21% (p < 0.001). There was a strong inverse correlation between HbA1c and muscle cross-sectional area (knee extensors) after the exercise period (r = -0.73; p < 0.05). Circuit resistance training seems to be feasible in moderately obese, sedentary elderly NIDDM subjects and the inclusion of circuit resistance training in exercise training programs for NIDDM subjects should be considered.