Summary:Planning for health and social services and for prevention programs requires predicting the number of AIDS cases likely to be diagnosed during the next several years and estimating the prevalence of HIV infection. Extrapolating from recent AIDS incidence data, we estimate that 365,000 AIDS cases will be diagnosed in the United States through 1992 (68% prediction interval, 205,000 to 440,000). Both recent HIV seroprevalence surveys and historical AIDS incidence are consistent with the U.S. Public Health Service estimate that 1.0 to 1.5 million persons in the United States are now infected with human immunodeficiency virus (HIV). Although current estimates of future AIDS cases and of current prevalence of HIV infection are somewhat uncertain, better statistical estimation procedures are being developed, and current surveys will provide additional data on HIV prevalence in the United States within the next several years.