4. Blood pressure higher than 145/90 after 10 minutes of rest, confirmed on two or more visits, or treatment with three or more antihypertensive agents at any blood pressure. Subjects taking up to two antihypertensive agents may be included in the study if 1) BP is at least 115/75 mmHg but < 145/90 mmHg on these agents and 2) they agree to remain on the same medications (and same dosages) during the study, unless otherwise advised by a primary care provider or study investigators (e.g. the dosage may be reduced or the medication may be stopped if signs or symptoms of hypotension develop during the study)