Clusters of cases of pneumocystis pneumonia and Kaposi’s sarcoma in New York and California in men who had sex with men were early harbingers of the acquired immunodeficiency syndrome (AIDS) epidemic. The syndrome was also soon noted to be associated with a high incidence of aggressive B-cell lymphomas. As the AIDS definition crystallized, Kaposi’s sarcoma, aggressive B-cell lymphomas, and invasive cervical cancer were considered to be AIDS-defining cancers when they developed in patients with human immunodeficiency virus (HIV) infection. Additional cancers are now known to be associated with HIV (Table 1). The term HIV-associated cancer is used here to describe this larger group of cancers (both AIDS-defining and non–AIDS-defining cancers) that have an increased incidence among patients with HIV infection. In addition, incidental cancers also may develop in patients with HIV infection.