Our objective was to determine the characteristics and survival of patients with non-Hodgkin's lymphoma (NHL) with and without acquired immunodeficiency syndrome (AIDS). A cancer registry and AIDS registry linkage for San Diego County was performed in October 1998 as part of a national multicentre study. We performed Kaplan-Meier analysis to compare survival in NHL patients with and without AIDS, after matching for age, sex, and race/ethnicity. We performed logistic regression to determine which patient and tumour characteristics were significantly associated with 1-year survival. Of the 4361 cases of NHL, 324 (7%) had AIDS and 4037 (93%) were not known to have AIDS. Patients with AIDS were more likely to have extranodal, high-grade, and disseminated NHL diagnosed by non-histologic means and were less likely to have received chemotherapy. Patients with AIDS and NHL who survived at least 1 year had less advanced disease stage and received chemotherapy. The median survival in patients with AIDS was 4 months (95% confidence interval (CI): 4-5) and 95 months (95% CI: 58-157) in patients without AIDS (P<0.001). Although these patients with AIDS-related NHL were unlikely to survive, the highly active antiretroviral agents currently used may improve outcomes in future patients.