To examine unexplored aspects of the association between AIDS and neoplasia, the Illinois AIDS and Cancer Registries were linked. The method integrated use of a personal computer to find exact matches on names and dates of birth with manual review to assure satisfaction of a match definition. Of the factors examined, white race and homosexuality predicted Kaposi's sarcoma (KS) among people with AIDS (PWAs), and white race predicted non-Hodgkin's lymphoma (NHL). Earlier reports of a declining proportion of PWAs with KS were confirmed. Lymphoma (mixed lymphocytic/histiocytic type), while not currently diagnostic of AIDS, occurred more frequently among PWAs than in the Illinois population. For the first time, rates of cancers other than KS and NHL were demonstrated to be significantly increased among PWAs compared with general populations. In the light of these findings, reconsideration of current neoplastic definitions may be useful.