Functional interleukin-2 receptors (IL-2R) on lymphocytes contain both IL-2R beta and gamma chains. Whereas constitutive expression of IL-2R beta has been found on monocytes, the expression of IL-2R gamma on these phagocytes has not been examined. We performed reverse-transcription-polymerase chain reaction with Southern blot analysis on RNA derived from purified human monocytes and discovered that they constitutively produce IL-2R gamma mRNA. Western immunoblotting revealed 58- and 64-kDa forms of IL-2R gamma on YT-1 and human monocytes, whereas 58-, 64-, and 69-kDa bands were detected using peripheral blood mononuclear cells and non-adherent lymphocytes. These different forms resulted from variable N-linked glycosylation since culture of the cells in tunicamycin resulted in detection of a single 39-kDa band which corresponds to the molecular weight predicted from the deduced amino acid sequence. By co-immunoprecipitation, the IL-2R beta subunit associates with only the 64-kDa IL-2R gamma protein band in monocytes.