Angiogenesis describes the formation of new blood vessels, which arise as outgrowths from existing vessels. In many physiological processes such as ovulation and wound healing angiogenesis is involved for a relatively short time. Otherwise under normal physiological conditions in the adult organism angiogenesis is an extremely slow process. By contrast in certain disease states such as diabetic retinopathy, arthritis, chronic inflammation, hemangiomas, etc., angiogenesis persists and contributes to the pathology of these disease states. Some 50 such "angiogenic diseases" have been described where angiogeneSiS is involved. Also in tumor growth and metastasis angiogenesis is an essential process and precedes neoplastic transformation. Hence, angiogenesis could become an important diagnostic tool and a target for developing therapeutic agents. This book contains the proceedings of the NATO Advanced Study Institute on "Angiogenesis in Health and Disease" held in Porto Hydra, Greece, from June 16-27, 1991. This meeting was a comprehensive review of endothelial cell biology and endothelial cell phenotypic and functional heterogeneity in relation to angiogenesis under physiological and pathological conditions. Numerous in vitro and in vivo models were presented, which are used to study angiogenesis at the molecular and cellular levels and to evaluate chemical compounds or naturally occuring substances for their effect on angiogenesis. The presentations and discussions at this meeting provided an opportunity for the basic science and the clinical disciplines to meet, exchange information and provide future research directions for many investigators engaged in the study of angiogenesis.