By the turn of the century 20-50 million adults are projected to be HIV positive in Asia, and India will have the largest burden of newly infected patients in a single country. To determine the present status of the epidemic, a systematic review of available data in India has been carried out. Regional differences in reported HIV seroprevalence were found, with high levels in western, northeastern, and southern India and lower levels in northern, central, and eastern India. While differences in the temporal introduction of HIV may be partly responsible, the more likely explanation is incomplete data and reporting. In the past 4 years HIV has rapidly increased among commercial sex workers and patients coming to sexually transmitted diseases clinics in western (Bombay) and southern (Madras and Vellore) India. Assessing HIV seroprevalence in the general population is difficult because of limited data, especially from rural areas, where 60% of Indians reside. Heterosexual contact with commercial sex workers is the major reported risk factor, except in eastern India, where intravenous drug use is common. The impact of transfusions or contaminated needles is uncertain, but between 25 and 75% of blood donations are not screened for HIV, and 15% of infected patients had received transfusions. By October 1993, 494 cases of AIDS had been reported, but this number grossly underestimates the real situation since HIV is often unrecognized. Tuberculosis is the major HIV-associated infection. In its efforts to control HIV, India needs to institute a standardized surveillance system to provide data needed to design and implement appropriate interventions.