It has been reported that the number of patients with hypertension increases yearly, and this imposes many anesthetic problems during surgery. The etiology of essential hypertension is unknown, but it affects primarily the brain, heart and kidney. The main causes of mortality due to hypertension are cerebrovascular accident, congestive heart failure, myocardial infarction and uremia. For the better anesthetic management of patients wuth hypertension, it is essential to clearly understand the pathophysiologic changes and hemodynamic patterns of hypertension. Because of the controversy regarding the appropriateness of preoperative treatment of hypertension, this article will evaluate the effect of preoperative antihypertensive medication on blood pressure during anesthesia of hypertensive patients. Patients with hypertension were divided into two groups, one group consisting of ll patients, who received antihypertensive medication in the preoperative period, and the other group, consisting of 11 patients, who did not received antihypertensive medication for the control of high blood pressure preoperatively. Changes of arterial blood pressure during anesthesia were analyzed, and data were compared between the two groups. The results were as follows: The patient who receivecd antihypertensisve medication for preoperative anesthetic management showed the same arterial blood pressure fluctuation during general anesthesia, as the patients who had not received antihypertensive medication (p < 0. 05). In the treated group, the blood pressure and heart rate changes during preinduction and intubation showed significant increase compared to the ward's values, but did not show a significant increase during operation annd recovery. In the nontreated group, the results showed similar changes with the treated group. It may be suggested from the above observation that the preoperative control of hypertension dose not affect the changes of blood pressure in the perioperative period.