The field of arteriosclerosis has undergone phenomenal development in recent years, as witnessed not only by increasing interest and expanding research but also by significant achievements toward understanding the nature of the process. This is as it should be, for this entity is the number one killer of Americans, middle-aged as well as elderly. Today we recognize that atherosclerosis is the hub of the arteriosclerosis problem. Once atherosclerosis is conquered, a tremendous dent in morbidity and mortality rates will follow and the average life span will be greatly lengthened. Progress in understanding has come first of all through rejecting the view that atherosclerosis is simply aging (senescence), which is inevitable and irreversible, and in accepting instead the idea that it is a disease and therefore preventable and (at least within limits) reversible; i. e., curable. The key to understanding the essence of the atherosclerosis problem lies in appreciating that it