The study was renewed in September 2000 to pursue two lines of investigation. The first was to identify and characterize genes contributing to atherosclerotic coronary heart disease using electron beam computed tomography (EBCT) to quantify coronary artery calcification as a measure of preclinical disease. Robust sibling-pair linkage methods were used to determine whether any of the more than 375 highly polymorphic tandem repeat marker loci spanning the genome were linked to genes influencing EBCT measures of coronary artery calcification in at least 500 GENOA sibships from Rochester, Minnesota. Association analysis was used to determine whether biallelic markers of DNA sequence variation in candidate genes identified by GENOA or others to influence blood pressure level or diagnostic category also influence EBCT measures of coronary artery calcification in at least 500 GENOA participants from Rochester, Minnesota. The second line of investigation extended analytical methods (linkage disequilibrium regression and combinatorial partitioning) to more finely localize positional candidate genes and loci, and to identifying gene-gene and gene-environment interaction effects influencing the measured Family Blood Pressure Program and GENOA phenotypes.