It is well established that endothelial dysfunction and insulin resistance go hand in hand. However, it is unclear if endothelial dysfunction per se is sufficient to impair insulin-mediated glucose uptake. We have previously reported that four weeks of administration of the HIV-1 protease inhibitor indinavir to HIV-negative subjects induces endothelial dysfunction. Hence, we hypothesized that indinavir-induced endothelial dysfunction was associated with impaired insulin-mediated glucose disposal. We measured insulin-mediated glucose disposal at the level of the whole body, skeletal muscle and vasculature, by performing hyperinsulinemic euglycemic clamp, and vascular function studies, in a separate group of HIV-negative, healthy non-obese subjects (n =13) before and after four weeks of daily oral indinavir. Four weeks of indinavir resulted in a 113±29% (p0.01) reduction of endothelium-dependent vasodilation, consistent with our earlier findings. In addition, there was a significant impairment of insulin-mediated vasodilation (101±14% pre-indinavir vs 35±15 % post-indinavir; p 0.05). However, there was no significant change in insulin-mediated glucose disposal at the level of the whole body (8.9±0.5 pre-indinavir vs 8.5±0.6 mg/kg/min post-indinavir; p=0.4), or skeletal muscle. Further, in a separate group of four HIV-negative, healthy non-obese subjects, we found that four weeks of indinavir has no sustained effect on insulin-stimulated glucose uptake in adipose tissue. Thus, our findings indicate that 1) endothelial dysfunction alone is insufficient to impair insulin-mediated glucose disposal, and 2) indinavir-induced endothelial dysfunction is likely due to a direct effect of the drug on the endothelium, and is not coupled to the induction of insulin resistance.