Research on chemical communication in animals is in a very active and exciting phase; more species are studied, data are accumulating, concepts are changing, and practical application seems feasible. While most of the work on chemical ecology and chemical sig nals deals with insects, vertebrate communication provides a formidable challenge and progress has been slow. Joint efforts and frequent direct contacts of ecologists, behaviorists, psychologists, physiologists, histologists and chemists are required. Such an interdisciplinary exchange of information took place on the occasion of the Symposium on Chemical Signals in Vertebrates and Aquatic Animals in Syracuse, New York, from May 31 to June 2, 1979. More than one hundred investigators from seven countries participated, and the papers presented comprise this volume. Since the first Symposium on Vertebrate Chemical Signals at Saratoga Springs in 1976, considerable progress has been made with field studies, the physiology of the vomeronasal organ, and its role in reproductive behavior. The behavioral functions and chemi cal nature of priming pheromones are better understood. Efforts to isolate and identify mammalian pheromones are gaining ground, and the bioassays are becoming more sophisticated. In addition to formal presentations, one evening of the Symposi um was devoted to round-table discussions of particular topics. The selected themes indicate the growing points of chemical communi cation research: priming pheromones, vomeronasal organ, bioassay, and practical applications.