The Japan Home versus Office Blood Pressure Measurement Evaluation (J-HOME) study was conducted to measure the control of blood pressure (BP) as evaluated by home BP measurement among 3,400 patients with essential hypertension (mean age: 66 years; females: 55%) receiving antihypertensive treatment in primary care settings in Japan. The purpose of this first report was to compare characteristics of BP control as measured at home and in the clinic (office) and define their association with BP control as evaluated by physicians. Mean systolic/diastolic BP (SBP/DBP) values were 140/82 mmHg for home BP and 143/81 mmHg for office BP. BP levels were not adequately controlled among approximately 60% of the patients, according to reference values described in the national guidelines (office BP: <140/90 mmHg; home BP: <135/85 mmHg). Even among patients evaluated by physicians as having excellent or fairly good BP control, office and home SBP values were insufficiently controlled in approximately 50%. Although the tendency was more remarkable among older patients, whose recommended target BP levels are higher than those of middle-aged patients in the Japanese Hypertension Society 2000 criteria, office and home BP values were not adequately controlled in approximately 50% of the middle-aged patients whose BP control was evaluated as good. Our findings suggest that an important reason why home and office BP values are not adequately controlled is that physicians approve relatively higher BP levels under treatment, even among middle-aged patients.