[Circadian rhythm variability in arterial blood pressure].

Summary Chrono-biology consists of the scientific study of biological rhythms and their underlying mechanisms. This study is based on the certainty that for many physiological variables these exists a reproducible pattern in the time of maximum and minimum values. The study of circadian rhythm variations on biological parameters which affect numerous pathologies permits one to foresee rhythmical cycles and to synchronize pharmacological rules to make it possible to obtain improvements in patients' responses. Knowing the circadian rhythm in hypertensive patients brings data related to the prognosis and is a basic tool to introduce the concept of a chronological administration of medicines in providing antihypertensive treatment; this is chronotherapy.