The range of changes in epidermal nerve fiber density (ENFD), subcutaneous fat, and mitochondrial function induced by stavudine (d4T)-based therapy is currently not known, globally or specifically in the Thai population. This study will evaluate ENFD and subcutaneous fat and peripheral blood mitochondrial parameters in 4 groups of subjects. Group 1 will include Thai HIV-positive subjects on long-term d4T treatment with symptomatic peripheral neuropathy. Group 2 will include Thai HIV-positive subjects on long-term d4T treatment without peripheral neuropathy. Group 3 will include HIV-negative subjects without peripheral neuropathy.Group 4 will include Thai HIV-positive subjects on long-term d4T treatment with asymptomatic peripheral neuropathy. Information gained from Thai HIV-positive subjects on long-term d4T treatment with and without neuropathy in this study will provide range of positive control values for subjects in the SEARCH 003 study and other studies looking at the influence of antiretroviral agents on peripheral nerve, fat, and mitochondria. Information gained from Thai HIV-negative subjects without neuropathy can be used as negative control values for subjects in the SEARCH 003 study and other studies looking at the influence of HIV or other diseases/pathogens on peripheral nerve, fat, and mitochondria.