The study of atherosclerosis centered since the first decade of the present century on etiology and pathogenesis. In fact, the studies of the military academy of medicine in St. Petersburg have opened the way of inducing atherosclerosis in animals. Pathogenesis of atheroma has been studied since then in humans and animals naturally prone to the development of the disease and by a variety of dietary and other procedures. The various experimental studies allowed science to evaluate the relative importance of different factors (genetic, dietary, hormonal, pharmacological, mechanical, circulatory, etc.) in atherogenesis. Epidemiological studies as well as biochemical plasma lipid and lipoprotein estimations coupled with light microscopic, histochemical and electron microscopic investigations decreased the gap between observations on the human and experimental animal research. The enormous literature covering this field allows the intelligent reader to formulate a comprehensive concept regarding etiological factors and pathogenesis of atherosclerosis. Its impact on preventive and curative medicine was however limited in scope. Study of atherosclerosis, the chief killer of adequately-fed populations, is of primary interest to physicians whose job is to prevent and treat illnesses. Thus, although theoretical considerations are of great interest and importance for a variety of reasons the main reason why humanity spends so much energy and money on the study of atherosclerosis is practical. The medical (including the scientific-medical) community, whose job it is to do its utmost to prevent or minimize the functional deficits, sufferings and mortality caused by atherosclerosis, is likely to pose the following questions at the head of its list of pressing problems: 1. Can atheroscleorosis be prevented and by what means? 2. Can it established atherosclerosis stops its progress, and can it regress? 3. Can regression, healing and/or scarring be of clinical significance in improving the perfusion of organs supplied by involved arteries? It is obvious that perfusion of organs depends, as far as the arteries are concerned, on two factors: elasticity of the vessel wall and the size of its cross section areas. The elastic properties of arteries are greatly deranged by the atherosclerotic process in all its phases and mainly in the stage of scarring or calcification. Elasticity of the arterial wall plays a minor role in the clinical phenomena in comparison to the effect of narrowing of the lumen. A major problem is, therefore, that of the effect of healing of the atherosclerotic process on organ perfusion. Healing by scarring associated with marked contraction of the vessel will obviously not be beneficial for organ perfusion Restitutio ad integrum or healing without reduction in size of the arterial lumen are the goals which scientists are trying to reach. Some attempts at reaching these aims, their limitations and inherent difficulties are reported in this book. Answers to these questions, however temporary and partial, are of cardinal importance. Medical scientists and practitioners are entitled to compact, understandable and, if possible, clinically applicable answers to these questions. It is the purpose of this small book to supply up to date knowledge regarding these points. The book is based on a symposium held within the framework of the Eleventh Triennial World Congress of Pathology in Jerusalem in late 1981.