Hormones, Brain and Behavior, Fourth Edition offers a state-of-the-art overview of hormonally-mediated behaviors, including an extensive discussion of the effects of hormones on insects, fish, amphibians, birds, rodents, and humans. Entries have been carefully designed to provide a valuable source of information for students and researchers in neuroendocrinology and those working in related areas, such as neuroscience, biology, psychology, psychiatry, and neurology. This fourth Edition has been substantially restructured to include both foundational information and recent developments in the field. Continuing the emphasis on interdisciplinary research and practical applications, the book includes articles aligned in five main subject sections. We propose maintaining several chapters, fusing some of the themes, and including new chapters on topics like alloparental behavior, depression and sexual behavior, neural plasticity, and sexual behavior, animal models to evaluate sexual orientation (including asexual orientation), effects of drugs of abuse and sexual behavior, adult neurogenesis and reproductive behaviors, neurobiology of sexual partner loss, mate choice. We propose to change the name of section 5 from “Development of Hormone-Behavior Relationships” to “Development and regulation of Hormone-Behavior Relationships”, which will better represent the topics covered in the 2 subsections “Early life stages” and “Later life stages”. Most of the chapters from the last Edition will be maintained in the new Edition. This reference provides unique treatment of all major vertebrate and invertebrate model systems with excellent opportunities for relating behavior to molecular genetics. The topics cover an unusual breadth (from molecules to ecophysiology), ranging from basic science to clinical research, making this reference of interest to a broad range of scientists in a variety of fields.