Interferon-gamma induces surface expression of interleukin 2 (IL2) receptors on human monocytes and the monocytic cell line U937. Freshly prepared peripheral blood monocytes and U937 cells were found to lack detectable IL 2 mRNA, but exposure of these cells to interferon-gamma induced IL 2 receptor message at 6 h of culture. At least two IL 2 receptor transcripts were detected (3.5 and 1.5 kb) in both monocytes and U937 cells, similar in size to IL 2 receptor transcripts in activated T cells. These results show that interferon-gamma induces expression of the monocyte IL 2 receptor gene.