&NA;Transcranial Doppler techniques were used to monitor blood velocity in cerebral arteries continuously during 14 neurosurgical operations performed on 13 patients, including 12 craniotomies. Stable Doppler signals were obtained for prolonged periods of time, and they correlated with intraoperative events. Monitoring during spontaneous blood pressure and CO2variations allowed assessment of autoregulatory capacity. In particular, 5 of the 7 patients receiving craniotomy for aneurysmal subarachnoid hemorrhage had impaired autoregulation. A 30 to 50% decrease in Doppler velocities was seen in 7 patients after etomidate administration. Early experience suggests that transcranial Doppler monitoring during craniotomy is feasible and can indicate the effects of operative events on blood flow as well as provide an assessment of cerebral autoregulation. (Neurosurgery25:769‐776, 1989)