IL-2 and IL-15 have overlapping functions since they share the IL-2R beta gamma receptor complex. However, each cytokine has a private a receptor namely IL-2R alpha for IL-2 and IL-15R alpha for IL-15. As a consequence the effects of the two cytokines may differ. We describe the differential effects of the two cytokines regarding the induction of cell surface expression of the IL-2R alpha subunit on YT-1 cells. Both cytokines induced transcription of the IL-2R alpha gene. Furthermore translation of IL-2R alpha leading to intracellular expression of the receptor was observed following either IL-2 or IL-15 addition. However, only IL-15 was associated with the induction of cell surface expression of IL-2R alpha. With IL-2 there appears to be an impediment to the translocation of IL-2R alpha to the cell membrane. Since surface expression of IL-2R alpha is a key element in the formation of the high affinity IL-2 receptor, translocation of IL-2R alpha to the membrane represents another level of control of the immune response in addition to regulation of IL-2R alpha transcription and translation.