Within 1 year of the initial report in 1981 of a deadly new disease that occurred predominantly in previously healthy persons and was manifested by Pneumocystis carinii pneumonia and Kaposi's sarcoma, the disease had a name: acquired immune deficiency syndrome (AIDS). Within 2 years, the causative agent had been identified: human immunodeficiency virus (HIV). On the 30th anniversary of the epidemic, to characterize trends in HIV infection and AIDS in the United States during 1981-2008, CDC analyzed data from the National HIV Surveillance System. This report summarizes the results of that analysis, which indicated that, in the first 14 years, sharp increases were reported in the number of new AIDS diagnoses and deaths among persons aged≥13 years, reaching highs of 75,457 in 1992 and 50,628 in 1995, respectively. With introduction of highly active antiretroviral therapy, AIDS diagnoses and deaths declined substantially from 1995 to 1998 and remained stable from 1999 to 2008 at an average of 38,279 AIDS diagnoses and 17,489 deaths per year, respectively. Despite the decline in AIDS cases and deaths, at the end of 2008 an estimated 1,178,350 persons were living with HIV, including 236,400 (20.1%) whose infection was undiagnosed. These findings underscore the importance of the National HIV/AIDS Strategy focus on reducing HIV risk behaviors, increasing opportunities for routine testing, and enhancing use of care (1).