We have investigated the frequency of Hind III DNA polymorphism of the human apolipoprotein B gene in a Canadian Caucasian population with coronary artery disease, as documented by angiography, and a healthy control population. Patients had significantly (p < 0.05) higher levels of cholesterol, triglycerides, LDL-cholesterol, apolipoprotein B, and lower level of apoAI compared to the controls. Restriction fragment-length polymorphism analysis detected nine hybridizable fragments denoted as H1 to H9. The H1, H2, H3, and H7 alleles were polymorphic. The [H4-H9] genotype seems to be the normal genotype within the population studied since it was detected in 69% of the control group. The [H1-H9] genotype was most frequently observed in the patients (frequency = 0.68). We were unable to strongly associate any of the alleles or genotypes detected with the changes in lipids. The additional alleles observed in the patient group may indicate possible mutations at the 3' end of the apolipoprotein B gene locus.