HIV-infected subjects on a stable protease inhibitor (PI) containing antiretroviral regimen with plasma HIV RNA <500 copies/mL, who have LDL cholesterol levels >130 mg/dL or fasting triglycerides levels >200 mg/dL, will be randomized (1:1) to continue their current antiretroviral regimen or to switch the PI to atazanavir (ATV). Brachial artery reactivity will be measured before (at entry) and 12 and 24 weeks after subjects are randomized.