This book is a compilation of the lectures and oral and poster communications presented at the Advanced Study. Institute on "Vascular Endothelium: Physiological Basis of Clinical Problems II," which took place between June 20 and 30, 1992 in Rhodes, Greece. This third in a series of ASIs on vascular endothelium continued on the theme of the first (1988) ASI on "Receptors and Transduction Mechanisms" and particularly expanded that of the 1990 conference on ''Physiological Basis of Clinical Problems. " We continued the successful practice of bringing together clinicians and scientists: this was reflected equally well in the composition of the organizing committee as in the background of the particiJ?ants. Endothelial cell functions and dysfunctions present as many challenges to the mvestigator as they do to the curious clinical practitioner. As these problems are necessarily different, this unique ten-day co-habitation of these individuals continued to offer fresh outlooks to each, stimulated potential collaborative efforts and, most importantly, advanced --ever so slightly--our knowledge of vascular biology. This year's conference was further enriched by the presence of several of our colleagues from Eastern Europe whom we are delighted to welcome as officially sponsored participants to this and future NATO-supported meetings. It is never superfluous to remind readers and participants that those signing at the bottom of this page, while responsible for many of the ASI's and the book's deficiencies, are but three of the many contributors to the successes.