The field of olfactory research and chemical communication is in the early stages of revolutionary change, and many aspects of this revolution are reflected in the chapters in this book. Thus, it should serve admirably as an up-to-date reference. First, a wide range of vertebrate groups and species are represented. Second, there are excellent reviews of specific topics and theoretical approaches to communication by odors, including chapters on signal specialization and evolution in mammals, the evolution of hormonal pheromones in fish, alarm pheromones in fish, chemical repellents, the chemical signals involved in endocrine responses in mice, and the controversy over human pheromones. Third, there are exciting new findings presented in numerous specific topic areas, such as the chemis try of pheromones in a wide range of species (salamanders to elephants), the chemistry of proteins that control the release of pheromones, the molecular biology and physiology of detection, coding and response to odor signals, the effects of experience on sensitivity to odors, the role of genes of the immune system in odor production and in human mate choice, the function and perception of scent over-marks, the recognition of individuals and kin by odors, the influence of odors on predator-prey interactions, and the use of odors to help control pests. This book is an offshoot of the Eighth International Symposium on Chemical Sig nals in Vertebrates, held at Cornell University in Ithaca, New York, July 20-25, 1997, hosted and organized by Bob Johnston.