Non-invasive ambulatory blood pressure monitoring allows to record numerous blood pressures during everyday activities. The relationship between blood pressure and target organ damage is closer with ambulatory than conventional office blood pressures. Monitoring blood pressure outside the doctor's office appears more and more useful in diagnosing and treating hypertension. This approach makes it possible to recognize high-risk hypertensive patients, i.e. patients exhibiting abnormally increased blood pressures in the presence as well as in the absence of the doctor.