AIDS-associated illnesses include Kaposi's sarcoma (KS), non-Hodgkin's lymphoma (NHL), and, since 1993, invasive cervical cancer (ICC). Between 1988 and 1998, among AIDS cases reported in western Europe, 9.6% had KS and 3.9% had NHL as AIDS-defining illnesses. Between 1988 and 1998, the frequency of KS decreased from 13.4 to 6.4%, while NHL increased from 3.8 to 5.3%. Estimates of the relative risk (RR) of neoplasms in HIV-seropositive populations came from population-based cancer and AIDS registries linkage studies conducted in the United States, Italy and Australia and from a few cohort and case-control studies. In adults with HIV/AIDS, the RR was over 1000 for KS and ranged between 14 for low-grade NHL and over 300 for high-grade NHL. For Hodgkin's disease (HD), a consistent 10-fold higher RR was observed. For cervical and other anogenital tumours associated with human papilloma virus, risk increases were 2- and 12-fold, depending upon location. In Africa, the AIDS epidemic led to KS becoming the most common cancer type in men in several areas. The RR of AIDS-associated tumours were lower in Africa than those reported in western countries.