Hypertension, diabetes, obesity, and aging are associated with increased arterial stiffness. Both insulin resistance and hyperglycemia may contribute to the development of arterial stiffness. Older nondiabetic hypertensive adults were recruited to test the following hypotheses: (1) insulin resistance is associated with arterial stiffness, and (2) this relationship is independent of glucose tolerance status. Aortic pulse wave velocity (PWV), pulse pressure (PP), insulin sensitivity index (S(I), measured by insulin-assisted frequently sampled iv glucose test), glucose tolerance status, and abdominal fat mass were assessed in 37 older (23 male, 14 female, mean age 69.4 +/- 5.9 yr), nondiabetic, hypertensive adults after a 4-wk antihypertensive medication withdrawal. Both PWV and PP were negatively correlated with S(I) (r = -0.49, P = 0.002, and r = -0.38, P = 0.02, respectively). The mean PWV and PP in those with normal glucose tolerance were not significantly different from those with impaired glucose tolerance (9.8 +/- 2.4 vs. 10.0 +/- 3.1 m/sec, P = 0.79 and 71 +/- 17 vs. 72 +/- 18 mm Hg, P = 0.80, respectively). In multiple regression analysis, PWV and PP remained independently correlated with S(I) (P < 0.05) after adjusting for age, gender, fasting glucose, glucose tolerance status, body mass index, or abdominal fat mass. These results suggest that in hypertensive, nondiabetic, older adults, insulin resistance is associated with arterial stiffness independent of glucose tolerance status.