The introduction of non-invasive, portable, automatic blood pressure measurement devices enables characterization of the blood pressure profile throughout the day in an ambulatory setting. The article advises against uncritical use. 24-hour ambulatory blood pressure measurements have become a valuable tool in scientific research, however, especially in studies dealing with antihypertensive efficacy. In hypertensive patients with "white coat hypertension", important data cannot be obtained without the use of 24-hour ambulatory blood pressure monitoring or blood pressure measurement at home.