Interleukin-2 (IL-2), secreted principally by activated helper T-cells, plays a pivotal role in the generation and regulation of the immune response. The various biologic functions of IL-2 have been the focus of intensive study over the years and have been well worked out. By contrast, an understanding of the intracellular signals coupled to the IL-2 receptor and responsible for mediating IL-2 effects in T-cells is far less developed, and the role that protein kinase C (PKC) may play in the various cellular responses to IL-2 receptor activation is unclear. In this article we will discuss IL-2, its receptors, and IL-2 signal transduction in relation to the physiological roles PKC activation may play in IL-2-mediated activation of T-cells and other hematopoietic cells.