Common carotid blood flow (CCBF) was measured in 11 anesthetised patients without extracranial arterial disease (nine acute subarachnoid haemorrhages and two cases of head injury). The range-gated Doppler flowmeter with an adjustable range-gated time system and a double transducer probe was used to determine diameter, blood velocity, and blood flow of the common carotid artery. Values were, respectively, 5.9 +/- 1.1 mm, 13.8 +/- 6.1 cm . sec-1 and 387 +/- 183 cm3 . min-1. Mean cerebral blood flow (rCBF) measurements were simultaneously made by 133Xenon intra-arterial method, with a value of 22.28 +/- 5.96 ml . min-1 . 100 g. High correlation coefficient was found between CCBF and mean rCBF (r = 0.73, p less than 0.001). The range-gated Doppler flowmeter thus provides a non invasive and easily duplicated method for monitoring cerebral blood flow in anesthetized patients.