As of February 2004, the government of India has agreed to provide HAART medication to HIV-infected individuals. Although the majority of HIV cases in India are due to heterosexual transmission, escalating drug use in selected regions of the country are associated with high rates of HIV infection. The primary drugs of choice in this drug-using population are heroin and buprenorphine. The study will enroll 100 HIV-positive and 100 HIV-negative drug-using clients who regularly attend Hopers Foundation, a network of drug treatment centers in Chennai. Hopers Foundation is a recognized presence in the drug use community, having worked for years with drug users in Chennai.