This study will provide the range of Epidermal Nerve Fiber Density (ENFD) typically seen in Thai individuals. ENFD values from Thai HIV-negative subjects without neuropathy will be used as appropriate reference norm for Thai HIV-positive subjects. In particular, comparison of ENFD values from Thai HIV-negative subjects with baseline ENFD values in Thai HIV-positive subjects prior to highly active antiretroviral therapy (HAART) will allow examination of the effect of HIV per se on ENFD. ENFD from Thai HIV-positive subjects on long-term d4T (stavudine) with and without neuropathy will also provide reference ENFD values at the extremes of the disease process i.e. extent of ENFD decrease in subjects with d4T-induced symptomatic neuropathy and in subjects completely free of disease despite d4T treatment for comparison with Thai HIV-positive subjects on short-term d4T in SEARCH 003 study.