The study used two well defined African populations from Nigeria to determine the contribution of 14 polymorphic genes involved in lipid metabolism in determining quantitative lipoprotein-lipid and apolipoprotein levels as these are major risk factors for coronary heart disease. The study also investigated how differences in life styles and dietary habits modulate the genetic contribution of these quantitative risk factors. Phenotypes in the gene products of APOs A-IV, C-II, D, H, J and (a) were determined by IEF and SDS/immunoblotting. Genotypes at the B,E, AI-CIII- AIV cluster, lipoprotein lipase, hepatic lipase, LDL-receptor, and cholesterol ester transfer protein were determined by polymerase chain reaction protocols. The quantitative levels of total cholesterol, HDL-cholesterol and its subfractions, HDL2- and HDL3-cholesterol, triglycerides and LP(a) were used in the genetic analyses. Estimates of the effect of alleles at each of the candidate loci on quantitative lipoprotein-lipid levels employed the measured genotype approach. The effect of multisite haplotypes for RFLP at various loci, where applicable, was also estimated using the same method. The interaction of alleles at various independent loci in determining quantitative lipoprotein-lipid and apolipoprotein levels was estimated. In addition to the measurements of environmental effects, measurements were also made of the genotype-environmental interaction in determining quantitative risk factor traits.