Twenty-four-hour monitoring of blood pressure (BP) is a new non-invasive technique of examination which, apart from becoming a useful research tool, has found widespread use in clinical practice. Monitoring detects BP fluctuations due to changes in physical and mental activities throughout the day and to physiological circadian rhythms, especially the nocturnal BP decrease. Monitored BP shows a better correlation with the degree of target organ damage than casual BP. In patients with increased BP values persisting despite therapy, BP monitoring makes it possible to differentiate hypertensives with truly resistant or inadequately treated hypertension from those showing substantially higher BP values in the doctor's office than their normal daytime levels are. BP monitoring may improve the accuracy of prediction of cardiovascular complications. This fact, however, has to be verified by other prospective studies which may expand the range of potential applications of this new method.