Recognition of the cytokine network as a mediator of numerous specific transduction systems has helped to revolutionize the study of immunology, cell biology, and the biochemistry of cell-to-cell interactions. The repertoire of interleukins (IL) and IL-mediated activities has expanded dramatically with the molecular cloning of distinct interleukin molecules. Interferon-gamma mediates many cell responses identical to those mediated by both interferon-alpha and -beta, such as induction of the antiviral state. The genus Chlamydia is composed of three species of obligate intracellular, prokaryotic pathogens, which have been further subgrouped into a number of distinct biovars. At the moment, however, the real problem that chlamydiae pose for the health and well-being of at-risk individuals does not involve treatment design, but rather recognition of the presence of chlamydiae in infected individuals. Finally, there are several nonviral diseases for which there are no known efficacious treatments. Individuals with South American trypanosomiasis, leprosy, and perhaps even cryptosporidiosis may benefit from treatment with Interferon-gamma.