Autopsies in 20 patients with the acquired immune deficiency syndrome (AIDS)-related lymphoma were studied retrospectively to ascertain the precise cause of death and the extent of lymphomatous disease. Eight patients had primary central nervous system (CNS) lymphoma: two of them were diagnosed antemortem; CNS lymphoma was suspected in three others by computerized tomographic (CT) scan and was confirmed at autopsy. The remaining three were diagnosed incidentally at autopsy. All had concurrent infections at autopsy, including opportunistic infection in six and pyogenic infections in two. Opportunistic infections at autopsy in these patients outnumbered those diagnosed clinically. Twelve patients had systemic lymphoma. Three were diagnosed only at autopsy, two of whom had extensive Kaposi's sarcoma (KS) as well. Eight patients were treated with chemotherapy, but died with disseminated disease. Opportunistic infections were found at autopsy in five patients. Secondary involvement of the CNS by lymphoma was frequent (66%) and was not related to previous bone marrow involvement. The authors conclude that the incidence of lymphoma occurring in AIDS may be more frequent than diagnosed clinically. Similarly, multiple opportunistic infections occur in these patients which are not diagnosed premortem and may contribute to early death.