This volume records the papers presented in Chieti, Italy, at the 1991 meeting of the International Society for Arterial Chemoreception (ISAC). This was the eleventh of a series of assemblies held since 1959. This field of research, which examines the critical function and mechanisms of O and pHIPC0 sensitive cells in 2 2 the body, is unique in that it encompasses diverse biological and medical areas. The reader of this book will note chapters concerning modem techniques like in situ hybridization; analysis of cell membrane channels and intracellular ion movements; immunohistochemistry of peptides, hormones, and the corresponding receptors of chemoreceptor cells; and systemic analysis of reflex pathways involving chemoreceptor cells and their meaning in health and disease. This broad spectrum will appeal to readers interested in the chemoreceptor field, as well as young scientists seeking a scientific field where not only structural analysis but also a sense for functional connections is required. In recognition of the importance of the contribution of a new scientific generation to this field, ISAC awarded the prestigious F. de Castro-C. Heymans E. Neil prize to A. G6rlach, a young scientist. Also at this meeting, the Ferdinando Data Foundation Award, for helping scientists from non-developed countries to pursue their interest in chemoreception, was initiated. ISAC held plenary lectures in honor of C. Eyzaguirre and R. Forster, both of whom have contributed greatly to research in the chemoreceptor field.