The acquired immunodeficiency syndrome (AIDS) epidemic has had a profound impact on our understanding of Kaposi's sarcoma (KS). Epidemiologic features suggest a sexually transmitted cofactor in the pathogenesis of AIDS-associated KS (AIDS-KS), and several putative agents have received intense scrutiny. Cell culture studies suggest that the angiogenesis of AIDS-KS is stimulated by both human immunodeficiency virus proteins and growth factors that may be involved in the development and progression of AIDS-KS, thereby providing a rationale for new therapeutic interventions. The dermatologist is uniquely qualified to provide care for the majority of patients with KS, as many patients have cutaneous lesions amendable to local therapy (cryotherapy, intralesional therapy, simple excision). Patients requiring more aggressive local therapy (radiation therapy) or systemic therapies (interferon, chemotherapy) can be easily recognized. Standardized staging criteria provide assistance for determining appropriate local or systemic therapy and for evaluating and comparing responses to new therapies. This article reviews the epidemiology, pathogenesis, histologic features, clinical spectrum, staging criteria, and treatment of KS.