Our most complete understanding of hormone receptor signaling may be exemplified in a family of hormones and receptors known as the cytokine superfamily. This volume is devoted to describing members of this hormone/receptor family from their molecular structures to their physiological effects. These hormones are not only biologically fascinating, but are also tremendously useful medicines.The first three chapters review the basic events in binding and signaling. The remaining papers present the cellular biology and physiological processes controlled by these hormones and receptors.