Pheromones (chemicals released by an organism that cause behavioral or physiological responses among members of the same species) apparently play an important role in the behavior of zooparasitic nematodes. These compounds may be essential for sexual communication prior to mating and, based on Nippostrongylus brasiliensis as a model, may also govern certain processes in the regulation of helminth population dynamics. Research will continue to investigate both biological and chemical aspects of the nematode pheromone communicative system. Biological studies will elucidate the helminth, host, and environmental factors that regulate or modulate phermone physiology. Chemical studies which are in progress will further isolate, purify, and characterize the pheromone components. Additional studies will examine the role of pheromones in the natural reproductive biology of Nippostrongylus brasiliensis and explore the possible effects of primer phermones in the regulation of developmental and/or physiological processes. Throughout the research, the data will be assessed from the perspective of designing feasibility studies that use pheromones as highly selective, biorational agents for disease control.