The network consists of five centers: two field centers, a rat genotyping center, a human genotyping center with statistical genetics and informatics, and a genetic analysis center. After genetic loci regulating blood pressure are identified, genomic markers are used to study genetic linkage with red blood cell lithium-sodium countertransport, hyperkinetic hyperadrenergic state, and the renin-angiotensin system in sibships and tested in several Black populations.