Endothelial dysfunction is a critical initial step of atherogenesis that subsequently contributes to the progression and clinical manifestations of atherosclerosis. The use of human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI) agents has been associated with increased cardiovascular events and worsening of multiple coronary heart disease risk factors including dys-lipidemia, insulin resistance, and endothelial dysfunction. Endothelial dysfunction may be caused by HIV infection itself as well as treatment-related effects of the antiretroviral agents used to treat HIV. The available evidence suggests that PIs may induce endothelial dysfunction via their effects on both lipid and glucose metabolism. Studies in healthy subjects confirm a role for reduced endothelial nitric oxide production in the endothelial dysfunction associated with the PI indinavir. Further work is needed to determine the relative tendencies of other antiretroviral agents to induce endothelial dysfunction, the physiologic mechanisms involved, and the contribution of the metabolic and body shape changes associated with HIV treatment-related lipodystrophy, and to establish effective interventions for endothelial dysfunction in HIV-infected patients.