THE National Health Survey found hypertension to be the most common chronic clinical disorder in the United States with a prevalence rate twice as large in the Negro population as in the white.1 One of the most common findings is a decrease in the blood pressure with bedrest alone. This led to early studies of blood pressure changes during sleep in patients with hypertension.2-8 By taking hourly readings, it was found that blood pressure fell during the night, reaching its lowest level in the early morning. More recently, the discovery of various sleep stages, as recorded electroencephalographically (EEG), and the discovery of two different physiological sleep states, rapid eye movement (REM) or dreaming sleep and nonrapid eye movement (non-REM) sleep, allowed closer examination of blood pressure changes during these phases of sleep. (In the literature, the following terms are approximate synonyms for REM stage sleep-dreaming