Hypertension Objective treatment based on Measurement by Electrical Devices of Blood Pressure Study (HOMED BP Study) is the first large-scale intervention trial in Japan using a Prospective Randomized Open Blinded Endpoint (PROBE) design to determine an optimal target blood pressure (BP) level on the basis of self-measured BP at home, and an optimal initial course of antihypertensive medication. The registered patients are randomized to either a more intensive BP-lowering group (home systolic BP < 125 mmHg and diastolic < 80 mmHg) or a less intensive group (home systolic/diastolic BP within the range 134-125/84-80 mmHg) by host computer via the Internet. The differential effect of three classes of initial antihypertensive regimens on the prognosis, i.e., calcium antagonist (Ca-A), angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin II receptor antagonist (ARB), which are used most frequently in Japan, are examined. Three regimens are also randomly assigned to the host computer via the Internet. A pilot study was started in May 2001. In March 2002, the number of participating doctors was 461. At the end of March 2002, 546 patients were recruited. Of these, 412 (202 men and 210 women, aged 58.4 +/- 10.2 y) were randomized. Patients will be recruited until February, 2006 and followed for 7 years.