Infection with MAC is a poor prognostic indicator in persons with AIDS. Evidence suggests that this poor outcome is not simply a reflection of greater immune impairment in AIDS patients with MAC infection, but rather may be a direct or indirect consequence of infection with mycobacterium. Survival of AIDS patients with MAC is shorter than those without MAC. Studies show that treatment for MAC improves the survival of MAC infected patients to nearly the survival of AIDS patients without MAC. Treatment of MAC with clarithromycin containing regimens is associated with decreased symptoms and prolonged survival. There is evidence, however, that mycobacterial infection may enhance propagation of the human immunodeficiency virus through mechanisms that may involve enhanced expression of pro inflammatory cytokines. It is unclear to what extent cytokine abnormalities contribute to this symptom complex and to what extent treatment of MAC infection will reverse these cytokine abnormalities.