"What we call the beginning is often the end, and to make an end is to make a beginning. The end is where we start from." T. S. ELIOT, "Geroniton" The discovery of endothelin-l was both an end and a beginning. It is an end because this discovery has started a plethora of investigations as to endothe1in's sites of production, mode of action, it's normal and abnormal physiological role and its involvement in a variety of pathological conditions ranging from renal failure to myocardial infarction, cardiac hypertrophy, hyperten­ sion, cyclosporine induced toxicity, mental depression, renal failure, stress related illness, and even stroke and sudden death. It is a beginning because no one can foresee where the investigations will ultimately lead, or how they will end. The discovery of the endothelins was a very recent event and soon specialist books will start to appear dealing in detail with different aspects of their chemistry, physiological role and pathological importance. The present book is intended to act as a guide and primer for those who are becoming intrigued by the many endothelin­ related articles which are now appearing in the journals but who as yet have not had the time or opportunity to be caught up in the web of enthusiasm and excitement which is motivating those more directly involved in the field of research.