During the past year, the most striking progress in our understanding of interferon-gamma has been made in the elucidation of the three-dimensional structure of the molecule and in the analysis of the molecular structure and the functional domains of the interferon-gamma receptor. A greater insight into the molecular mechanisms of gene activation by interferon-gamma has been gained, and the immunoregulatory role of interferon-gamma has been better defined in studies dealing with its effects on B-cell function and with its production by the various T-cell subsets. Finally, the effects of interferon-gamma on intracellular parasites is an important aspect of interferon-gamma activity that is giving rise to several clinical trials.