WHEREAS the studies of coronary heart disease in the first half of this century have emphasized the pathology, pathologic physiology, and clinical features, there has been increasing emphasis on preventive aspects during the second half of the century. The beginnings were halting and random, mainly because they related to a limited investigative base. Since the early 1950s, however, there has been a steady increase in new knowledge of the epidemiology of coronary atherosclerosis and its complications. This new information provided a more substantial base for consideration of prevention, and resulted in many recommendations for application either to individual patients or the public in general, recommendations which were not, however, universally accepted or applied. That an emphasis on prevention was highly appropriate was not an issue. The magnitude of the problem of atherosclerosis generally and of heart disease due to coronary atherosclerosis in particular was clearly overwhelming and frightening. CONTROVERSIAL ISSUES