Chronic ethanol ingestion predisposes to tuberculosis and bacterial pneumonia. Mycobacterium avium complex organisms cause bacteremia in patients with AIDS. Human macrophages and murine Kupffer cells exposed to ethanol are more permissive towards intracellular growth of M. avium than control mononuclear phagocytes. Ethanol also has been shown to impair the ability of human macrophages and murine Kupffer cells to respond to stimulation with tumor necrosis factor (TNF) and granulocyte macrophage colony stimulating factor (GM-CSF), and to produce cytokines such as interleukin-1, interleukin-6, and TNF when properly stimulated. The impairment is dependent in part on a downregulation in the number of TNF receptors on the macrophage's membrane. Recent evidence suggests that ethanol in nonlethal concentrations induces stress-related proteins in M. avium, leading to the inhibition of intracellular pathways in the macrophage and, consequently, impairing some of its functions. In summary, ethanol acts both on the host and on the mycobacterium in a complex sequence of events that influence the outcome of the infection.