Five men developed disseminated infection with Mycobacterium avium-intracellulare. These patients all lived in the New York City area and presented with their illnesses between January 1981 and September 1981; four were homosexual and one was an intravenous drug abuser. Four patients died. All five patients had defects in the cell-mediated immune response. The infections were characterized histopathologically by poor or absent granulomatous tissue reaction. Clinical isolates of M. avium-intracellulare from all five patients agglutinated commonly used antimycobacterial drugs. The spectrum of opportunistic infections among populations of homosexuals and drug abusers should be expanded to include disseminated disease due to M. avium-intracellulare.