Basilar artery (BA) injury has been reported in a number of cases as a major complication of third ventriculostomy for hydrocephalus. This report describes the deployment of a pulsed-wave microvascular Doppler probe through the endoscope to locate the BA complex and subsequently to select a safe zone for perforation of the third ventricular floor. This procedure is quick and easily learned, and it is hoped that it can decrease the risk of vascular injury during third ventriculostomy.