Blood velocity in the anterior spinal artery was measured with a 20 MHz doppler ultrasound microvascular probe through a standard laminectomy during syringoperitoneal shunt placement. Velocity increased with increasing levels of pCO2, with dural opening, and with syrinx drainage. These observations support the use of the doppler signal as an index of arterial blood flow. Doppler measurements are easily performed, do not require dural opening, and may be performed repetitively without risk of tissue damage. Pulsed doppler techniques provide a rapid, safe method for intraoperative evaluation of spinal cord blood velocity and may emerge as a useful tool for assessment of spinal cord blood flow.