Inspite of several doubts and controversy, there is overwhelming evidence that high blood cholesterol is associated with an increased risk of coronary heart disease, and furthermore, that the association is not merely coincidental but causative. Gaps remain, to be sure, in the understanding of how diet, cholesterol, and atherosclerosis interrelate, and research continues to fill those gaps. Meanwhile, ample data from vastly different types of research support the theory that high cholesterol levels in the blood are associated with increased risk.