The study might shed important light on the variation in patient response to antihypertensive agents, and improve the ability to pick the right antihypertensive for specific patients. GenHAT is an ancillary study to ALLHAT (the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial). ALLHAT recruited 42,515 hypertensives and randomized them to one of four antihypertensive agents (lisinopril, chlorthalidone, amlodipine, and doxazosin); follow-up will be completed in March, 2002.