Spontaneous changes in blood pressure (BP) over a week after admission to the hospital were investigated in 127 patients admitted with diastolic BP at or above 120 mm Hg. Average BP decreased from 205/129 at admission to 174/110 on the 8th day. Regression analysis showed highly significant negative slopes which were related to initial levels but not to the presence or type of target organ involvement. After 1 week, 66% of the subjects attained a diastolic BP lower than 120 mm Hg. More remarkably, 36% attained values lower than 105 mm Hg; 33% of these had BP values less than 95 mm Hg.While not ruling out the importance of very high BP readings, it is concluded that they do not necessarily represent any pattern of either fixed or severe hypertension nor imply a need for urgent antihypertensive treatment.