The existence of endothelium-dependent hyperpolarization and endothelium-derived hyperpolarizing factor was established during 1997 at an international symposium held in near Paris. This further volume reinforces the concept that EDHF, as opposed to nitric oxide (NO), is of particular importance in smaller blood vessels and, in addition, underlines the multiplicity of other factors involved. Many candidate mentors are discussed, including some new, sometimes surprising ones and the actions of EDHF on vascular vascular smooth muscle cells are detailed, almost down to the molecular level. Further chapters enlarge our knowledge of the physiological and pathological roles of endothelium-dependent hyperpolarizations, and the book concludes with reports on the still limited but crucial knowledge of the contribution of EDHF in human blood vessels in health and disease.