Two GENOA cohorts were originally ascertained (1995-2000) through sibships in which at least 2 siblings had essential hypertension diagnosed prior to age 60 years. All siblings in the sibship were invited to participate, both normotensive and hypertensive. These include non-Hispanic White Americans from Rochester, MN (n =1583 at the 1st exam) and African Americans from Jackson, MS (N=1854 at the 1st exam). During the second exam (2000-2005), approximately 80% of participants were re-recruited.

Individuals in GENOA belong to sibships identified in which at least two siblings had essential hypertension diagnosed prior to 60 years of age. *After identification of the initial pairs of hypertensive siblings, *all siblings* in the sibship were invited to participate regardless of hypertension status.*

*Hypertension case definition:* Essential hypertension diagnosed prior to age 60 years of age, defined as: 1) average of the last 2 out of 3 systolic BP readings ≥ 140mmHg, or 2) an average of the last 2 out of 3 diastolic BP readings ≥ 90 mmHg, or 3) previous diagnosis of hypertension and antihypertensive medication prescribed by a physician to be taken daily during the last month.

*Exclusion criteria:* Pregnancy or breast feeding, Type I diabetes mellitus (juvenile onset, insulin dependent), diagnosis of hypertension ≥ 60 yrs of age, or secondary causes of hypertension including but not limited to prior knowledge of renal parenchymal disease or serum creatinine ≥ 2.5 mg/dL, renal vascular disease, primary aldosteronism, pheochromocytoma, coarctation of aorta, hypertension associated with current use of oral contraceptive agents, prescription or non-prescription drugs, or active alcohol abuse.