A major component of the prevention and treatment of coronary heart disease is the attenuation of its major underlying process, atherosclerosis, which brings about myocardial ischemia. In exploring the determinants of atherosclerosis, a diet-heart hypothesis has emerged. Simply stated, the hypothesis is that the excessive ingestion of dietary fat, notably total fat, saturated fat and cholesterol and lowered intakes of other nutrients including unsaturated fatty acids and possibly soluble fiber lead to the elevation of serum LDL-cholesterol which causes atherosclerosis. Support of the diet-heart hypothesis is available from epidemiologic, laboratory, and clinical research.