This protocol is designed to determine whether there is a pathologic effect on endothelial function from the lopinavir/ritonavir. By measuring endothelial function in HIV non-infected subjects both before and after four weeks of therapy, we will be able to investigate whether the medications have a direct toxic effect on the endothelium. Collection of metabolic data will allow us to evaluate whether endothelial function occurs in conjunction or separate from lipoprotein and glucose metabolic changes. As ARV options increase, it may be possible to choose specific regimens that may minimize acceleration of cardiovascular risk factors associated with endothelial dysfunction, especially in patients with other cardiovascular risk factors. These findings may help elucidate the pathophysiology of premature cardiovascular disease in HIV positive patients and also plan interventions to minimize endothelial dysfunction and subsequent cardiovascular disease.