Highly active antiretroviral therapy (HAART) has proven effective in altering the natural history of HIV infection in many patients. However, this therapy may not be sustainable because of the toxicities of the medications. Evidence suggests that HIV-infected patients on HAART may be at risk for premature coronary artery disease. The exact cause is unknown. It is possible that the medications directly affect the endothelium (the lining of the arteries that supply blood to the heart) and lead to premature heart disease. Or because the medications cause lipid abnormalities (high cholesterol) and a condition of relative insulin resistance, in which the body has a difficult time processing sugars; known risk factors for endothelial dysfunction and heart disease. Therapeutic intervention that reverses these lipid abnormalities and/or insulin resistance may lower these risk factors, normalize endothelial function, and decrease the risk of heart disease.