Five homosexual men dying at UCLA Center for the Health Sciences, Los Angeles, with acquired immunodeficiency and Pneumocystis pneumonia, Kaposi's sarcoma, or cryptosporidiosis since May 1981 have all had mycobacteria of the Mycobacterium avium-intracellulare complex cultured from tissues taken just before death or at postmortem examination. Each man had histological evidence of disseminated mycobacterial infection. Acid-fast organisms were seen in macrophages in the lung, spleen, and lymph nodes in all cases and in a variety of additional organs in two cases. Other severe infections were always found at postmortem examination — cytomegalovirus, cryptosporidiosis, and Pneumocystis. Disseminated M avium-intracellulare infection has been so striking in homosexual males dying with acquired immunodeficiency at our institution that we believe a vigorous search for mycobacteria should be made in all such patients. Empiric therapy for mycobacterial infection may be justified in selected cases of immunodeficiency before a specific microbiological diagnosis.