The human immunodeficiency virus (HIV) pandemic has infected 56 million persons worldwide, including 20 million who have already died. An estimated 1.1 million persons in the United States have been infected with HIV. In the 3 years following the introduction of highly active antiretroviral therapy (HAART), mortality, AIDS, AIDS-defining diagnoses, and hospitalizations all decreased 60% to 80%. Despite the absence of a cure, the natural history of the disease has radically changed.