Despite progress in the treatment of HIV and a greater understanding of the pathophysiology of HIV infection, there are still unexplained differences in both the progression of untreated HIV infection and response to antiretroviral therapy. These differences are likely related to the unique genetic makeup of individuals with HIV infection. Particular genes may offer protection against HIV infection, while other genes may make disease progression more likely. Knowing more about the genetic makeup of HIV infected individuals may lead to the development of a targeted treatment strategy based on an individual's specific risk of disease progression and sensitivity to medication toxicity. The purpose of this substudy is to collect blood samples from SMART study participants. The samples will be used in future Community Programs for Clinical Research on AIDS (CPCRA) studies investigating the link between human genetic factors and clinical outcome data.

This study will enroll individuals currently participating in the SMART study. Participants will provide one blood sample. Individual test results from future blood analyses will not be provided to a patient unless they may have profound health implications for that patient.