We linked records of 83,434 AIDS cases reported to AIDS registries through I990 to cancer registry records during times when overlap in registration existed. Of 8,496 Kaposi's-sarcoma (KS) cases meeting enrollment criteria, 1,045 occurred semesters 2 through 4 (6 through 23 months) after another AIDSdefining illness. KS risk in this period after AIDS declined steadily over the 1980s. Adjusting for age, gender, ethnic origin and calendar time period, we found the relative risk (RR) of KS to be I06,OOO for homo/bisexual men with AIDS and I3.000 for other men with AIDS. Risk was highest for homo/bisexual men between 30 and 39 years old and among 20-to 29-year-old non-homo/bisexual men. The RR in black men was approximately half that reported in white men among homo-bisexual men and others. Between the second and fourth semester after AIDS, the ratio of RR of KS to that of non-AIDS-related cancers increased 1.5-fold. In a similar analysis, there were 335 non-Hodgkin's lymphoma (NHL) cases in semesters 2 through 4 after AIDS. The overall risk was elevated 283-fold in homo/ bisexual men and the RR ratio increased 1.8-fold between semester 2 and 4 after AIDS. In summary, the risk of KS following another AIDS-defining illness is strikingly high, more in white men than in black men, and the risks of KS and, especially, NHL appear to increase with time from AIDS. o 1996 Wiley-Liss, Inc. * Kaposi's sarcoma (KS) and non-Hodgkin's lymphoma (NHL) are diseases indicative of AIDS in persons with humanimmunodeficiency-virus (HIV) infection (Centers for Disease . Homo/biscxual men with HIV infection have