Hormones strongly influence and even "drive" certain primitive behaviors. In , Richard J. Bodnar, Kathryn Commons, and Donald W. Pfaff examine hormonal, neural, and genetic mechanisms of reproductive, pain-sensing, and pain-inhibitory systems. The authors show that there are remarkable neuroanatomical, biochemical, and functional overlaps among these systems. They consider sensory inputs triggering both classes of behaviors and focus on the role of sex hormones in modulating both forms of behavior. Sex hormones acting in different regions of the brain not only energize reproductive behaviors but also modulate opioid-dependent pain-inhibitory pathways. The authors also summarize some intriguing gender differences in hormone actions and responsivity to pain. The clinical implications of this field of research are numerous. will appeal to anyone interested in new ways of looking at behavioral dispositions as they are influenced by specific genetic, neural, and hormonal states.