Hyperapo B is a phenotype defined as elevated plasma level of the major apoprotein B of low density lipoproteins in the presence of a normal plasma level of low density lipoprotein cholesterol. It has been demonstrated that hyperapo B is strongly associated with coronary artery disease. In 1984 when the study began, the independence of this association with other risk factors for coronary artery disease such as cigarette smoking, hypertension, and low plasma levels of high density lipoproteins was not known. The study improved knowledge of the pathophysiology of coronary artery disease and of the genetic and biochemical defects of hyperapo B and hypoalphalipoproteinemia.