The study was renewed in FY 2000. To further elucidate the environmental pathways, the investigators conducted a substudy cross-classifying participants on the major risk determinants (ie, obesity and sodium intake) and they examined gene-environment interactions directly. They used a genome scan in linkage analysis to identify new chromosomal regions of interest. They also examine two new candidate loci (adducin and beta-2 adrenergic receptor) and conducted association studies using single nucleotide polymorphisms. They used the full range of analytic tools, including segregation, linkage and cladistic analysis.