Atherosclerosis is a multifactorial disease. There are many theories surrounding its pathogenesis, none of which is more popular than the "lipid" hypothesis. There is an extensive body of evidence from experimental, epidemiological and pathological studies linking diet to plasma cholesterol on the one hand and plasma cholesterol to heart disease on the other. These data suggest strongly that education of the public about diet modification as one means of reducing CHD risk is a safe, appropriate and feasible approach to the prevention of the disease at the present time. The recommendations to the public are to reduce the fat content of their diets, specifically saturated fats, and limit the daily intake of dietary cholesterol to 300 mgs/day.