HIV-1 evolves rapidly and multiple genetic subtypes have been isolated from a number of geographic locations. There are limited data on the distribution of subtypes in the Southern African HIVNET sites. Data suggest subtype C HIV-1 predominates and this study is designed to substantiate and extend these observations to understand the biological relationship between HIV-1 subtypes, genetic variability, and immune responses. Earlier studies were conducted using individuals who had been seropositive for 3 to 9 years with advanced disease status; this study will test reactivity during the early stage of infection. This will assist in the rational selection of prototypic isolates for inclusion in either a single universal vaccine or vaccines tailored for specific subtypes/geographical regions.