 Endothelial dysfunction, assessed by measurement of brachial artery reactivity, is associated with coronary artery disease. Previous studies showed that patients taking HIV protease inhibitors PIs had a buildup of fatty deposits in their arteries and impaired flow-mediated vasodilation of the brachial artery, whereas endothelial function was normal in HIV-infected individuals not taking PIs. The effect of three different antiretroviral regimens on endothelial function in antiretroviral naïve HIV-infected patients will be examined in this substudy. 