Cardiovascular disease remains the primary cause of mortality in patients who are maintained on hemodialysis. Arterial stiffness and insulin resistance are independent risk factors for cardiovascular mortality in this population. In healthy individuals, higher physical conditioning is associated with reduced arterial stiffness. Exercise reduces insulin resistance and glucose intolerance in sedentary, overweight individuals and diabetic patients. The purpose of this study was to determine the impact of an exercise program on arterial stiffness and insulin resistance in a group of patients on hemodialysis. The effect of exercise training on arterial stiffness and insulin resistance in 11 patients who were on chronic hemodialysis was evaluated. Exercise classes of 1-h duration were conducted twice weekly for 3 mo. Arterial stiffness was assessed using the radial artery pressure waveform analysis. Aerobic exercise improved arterial stiffness from 17 +/- 3 u at baseline to 12.2 +/- 3 u at the end of the intervention (P = 0.01). After 1 mo of detraining, arterial stiffness reverted to pre-exercise levels (17.3 +/- 3 u). Pulse pressure paralleled arterial stiffness changes, and the correlation between them was statistically significant (r = 0.725, P = 0.012). Insulin resistance was calculated using the homeostatic model assessment formula. Exercise at the intensity and duration used in our study had no impact on insulin resistance (P = 0.38). These findings suggest that 3 mo of aerobic exercise training improves arterial stiffness, an independent risk factor for cardiovascular mortality in patients who are on hemodialysis, and has no impact on insulin resistance. The beneficial effect on arterial stiffness dissipates within 1 mo of detraining. To obtain therapeutic benefits, an exercise program for patients who are maintained on hemodialysis should be designed to promote regular long term exercise, >3 h/wk.