Kaposi's sarcoma (KS), one of the first conditions to be recognized as an opportunistic sequela of infection with the human immunodeficiency virus type 1 (HIV), remains the most common neoplasm associated with acquired immunodeficiency syndrome (AIDS). Over the past 15 years, considerable progress has been made in describing its epidemiologic and clinical features, in elucidating its pathobiology, and in developing therapeutic approaches. Despite therapeutic advances, the treatment of KS remains palliative, but a clearer understanding of KS pathogenesis holds promise for eventual curative or even preventive therapy. This article reviews current knowledge about the epidemiology, natural history, pathogenesis, and treatment of AIDS-associated KS and considers future therapeutic opportunities.