AIDS (acquired immunodeficiency syndrome) was first reported in the United States in 1981, and has since become a major worldwide epidemic. AIDS is caused by HIV (human immunodeficiency virus). More than 900,000 cases of AIDS have been reported in the United States since 1981. As many as 950,000 Americans may be infected with HIV, one-quarter of whom are unaware of their infection. The epidemic is growing most rapidly among minority populations and is a leading killer of African-American males ages 25 to 44. According to the Centers for Disease Control and Prevention (CDC), AIDS affects nearly seven times more African Americans and three times more Hispanics than whites. At Hopkins, general internists work closely with their colleagues in infectious disease to treat and investigate HIV/AIDS with particular attention to 1) the organization, costs, and quality of care; 2) comorbid medical and mental illness in people with HIV/AIDS; and 3) metabolic complications of antiretroviral therapy.