In Project 1, gene mapping is performed on genes that influence quantitative phenotypes related to the development of atherosclerosis in Mexican American families in the San Antonio Family Heart Study. A genomic search using a 10 centimorgan map of 3 91 short tandem report markers distributed throughout the genome is used to determine the chromosomal location of six major genes influencing HDL cholesterol, LDL cholesterol, apo A1, apob, SHBC, and DHEAS. Evidence for major gene effects is sought for lipoprotein phenotypes for which no major genes have yet been detected. Genetic effects on carotid and fibrinolysis phenotypes are quantified using data from a recall of 750 family members. Full pedigree variance component analysis as well as penetrance-based methods are used in a genomic search to determine the chromosomal locations of genes that influence these phenotypes. To improve genetic models, strengthen evidence for linkage, and reduce the number of false positives, GxE interactions and pleiotropic and epistatic effects of major genes are quantified.