In this case-control study, the study population consisted of incident cases who presented to the Georgia Heart Clinic in La Grange, Georgia with coronary heart disease. The majority of the subjects were from three counties in mideastern Alabama and from counties in midwestern Georgia. All subjects had undergone diagnostic coronary angiography. A determination was made in patients and controls of the association of major histocompatibility complex genetic markers HLA-A, -B, -C, -DR, C4 and BF, C3, the restriction fragment length polymorphisms (RFLP's) flanking the apolipoprotein AI and insulin genes, presence of autoantibodies, and family history of coronary disease, diabetes, or hypothyroidism. The frequency of these variables was compared with the standard coronary risk factors of family history, hypertension, lipid abnormalities, lifestyle, Type A behavior, obesity and with diseases such as diabetes and hypothyroidism. An analysis was made of the strength of these variables for predicting those individuals at risk and whether there were variables which predict severity of disease based on 1, 2, or 3 vessel involvement.