Each collaborating investigator is responsible for an essential element of the network: Eric Boerwinkle for genotyping and linkage analyses, Robert Ferrell for genotyping, Craig Hanis for recruiting Mexican-Americans, Richard Hutchinson for recruiting African-Americans, Sharon Kardia for cladistic and prediction analyses and data management, and Stephen Turner for recruiting Non-Hispanic whites and measuring physiologic variables. Between 1995 and 2000, the network carried out five specific aims to localize and characterize the genetic determinants of high blood pressure. Aim 1 used robust sibling pair linkage methods in 500 hypertensive sibling pairs in each racial group (a total of 1,500 sibling pairs) to localize genes influencing interindividual differences in the occurrence of essential hypertension. Aims 2 and 3 took advantage of previously collected blood pressure and intermediate predictor trait data from 1,488 normotensive sibling pairs from the Rochester Family Heart Study to localize genes contributing to essential hypertension. The linkage analyses (Aims 1-3) used both an extensive array of candidate genes and a large number of anonymous markers throughout the genome. Aim 4 used multiple diallelic sequence polymorphisms and cladistic analyses within a linked gene to identify haplotypes for further DNA sequencing in order to identify candidate functional DNA sequence variation contributing to interindividual differences in BP levels and essential hypertension status. Aim 5 evaluated the ability of candidate functional DNA sequence variation to predict essential hypertension status in the three racial groups.