To evaluate the self-measurement of blood pressure at home, a comparative study was performed among home (Home BP), ambulatory (24-hour BP) and office blood pressure in essential hypertensive patients. In all patients, Home BP was self measured by themselves twice a day for a month. 24-hour BP was measured once during the period of self-Home BP measurement. Office BP was measured twice a month. The average of Office BP (147/92 mmHg) and Home BP (145/89 mmHg) were higher than the average of 24 hour BP (131/82 mg). For systolic BP, about two weeks self-measurement of BP at home just after waking elicited a very high correlation between home and average 24-hour BP (r = 0.82), whereas for diastolic BP the r value was moderate (r = 0.61). In patients (n = 22) treated with antihypertensives, furthermore, the correlation coefficient between home and 24-hour BP for systolic BP reached 0.89, which is higher than in all patients (n = 28). The average value of BP measured just after waking at home elicited a higher correlation with the average value of 24-hour BP compared with that measured before going to bed. The results suggest that in essential hypertensive patients who are treated with antihypertensives, to measure BP just after waking for about two weeks at home could help clinicians to evaluate and predict the value of average 24-hour BP.