 NRTIs are a mainstay of HIV treatment regimens, often part of initial treatment regimens for newly diagnosed patients. Recent data suggest that NRTIs are responsible for lipoatrophy, a condition marked by progressive fat loss. Another negative side effect to antiretroviral ARV regimens is mitochondrial toxicity, which can damage the heart, nerves, muscles, kidneys, pancreas and liver, as well as affecting the bodys ability to produce energy for important life processes. It has been hypothesized that lipoatrophy may be related to mitochondrial toxicity, but a causal relationship between the two has yet to be established. This study will examine HIV infected treatment-naive patients who are initiating their first ARV regimens. The regimens will contain 2 NRTI, one of which being zidovudine and a non-nucleoside reverse transcriptase inhibitor NNRTI. The regimens will not contain any PIs. 