Hypotensive anesthesia is still widely employed during neurosurgery in spite of the development of microsurgical techniques. There have been a few reports regarding cerebral blood flow during injections of labetalol, a non-selective beta and selective alpha 1-blocker, to control blood pressure during or after craniotomy and results were favorable. In 4 cases, intermittent labetalol injections were given for hypotensive anesthesia during clipping of a cerebral aneurysm and the results were as follows: 1) The onset was within 1-2 minutes after injection. 2) Hypotensive anesthesia was well maintained by repeated injections during surgery. 3) Systolic and mean arterial blood pressure were decreased as much as 35.7 mmHg and 24.3 mmHg respectively. 4) Heart rate did not change significantly. 5) After clipping, blood pressure returned to the previous level with atorpine or ephedrine. 6) We conclude that labetalol can be an excellent choice for hypotensive anesthesia.