In 1980 a series of biochemical and physiological tests were initiated in the 2,548 persons in 98 extended pedigrees in Utah. Most of the subjects were obtained from three major pedigree types: stroke cluster pedigrees; coronary heart disease cluster pedigrees; and pedigrees of Utah Hypertension Detection and Follow-up Program high blood pressure probands. Data were collected on personal history, medical family history and genealogy, anthropometrics, standard and 32-lead electro- cardiograms, multiple blood pressure measurements during sitting, standing, lying, tilting, isometric hand grip exercise, bicycle exercise, venipuncture and mental arithmetic. Cation tests included sodium-lithium countertransport, lithium-potassium co-transport, intracellular sodium, potassium, magnesium, sodium-potassium ATP-ase pump activity and binding sites and plasma levels of sodium, potassium, magnesium, ionized calcium and digoxin-like pump inhibitor. Information was also collected on stress, exercise, plasma renin activity, and urinary kallikrein. Statistical and pedigree analysis were conducted.