Although coronary heart disease has long been known to aggregate in families, in 1986 little was known about the relative importance of genetic and environmental factors. This was partly due to the heterogeneous nature of the disease. Instead of analyzing complex endpoints, the tendency had been to focus on the individual risk factors or phenotypes. Plasma lipids and lipoproteins are heterogeneous risk factors that have been analyzed as subgroups from a genetic epidemiological perspective. Attention turned to the familial aggregation of risk factors, particularly the hyperlipidemias, hypertension, and diabetes.