The GenNet Network was renewed in September 2000 to continue studies of hypertension-associated phenotypes in United States whites, African Americans, Mexican Americans, and West Africans and Caribbeans. The Family Blood Pressure Program as a whole carried out five specific aims in the renewal period. These aims were grouped according to two complementary themes: First, the investigators created and analyzed a database of blood pressure-related phenotype and genotype data from all FBPP participants (Aim 1). Within linked regions, they identified allelic variation within positional candidate genes and evaluated the relationship of these polymorphisms with blood pressure levels and hypertension status (Aims 2 and 3). Second, they used quantitative measures of target organ damage to identify genes that influenced susceptibility to develop hypertensive heart and kidney diseases (Aims 4 and 5). In addition to the Program specific aims, each network, including GenNet, carried out its own specific aims alone, based on unique aspects of their population and interests and expertise of the investigators. In GenNet, progress has been made in the identification of single nucleotide polymorphisms (SNPs) in candidate genes and work was underway to develop rapid genotyping methods in individual and pool samples. The search for genes in diverse human populations was complemented by mapping studies in rat strains, in which linked regions that overlap with regions showing evidence for linkage in the human studies were selected for positional cloning.