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Aim: To quantify the volume flow rate- (VFR-) effects of internal carotid disease on the common carotid artery both ipsi- and contralaterally for various degrees of stenosis., Method: A non-invasive ultrasonic time domain processing (M-mode) was used. This proved to be reproducible in vivo and accurate in vitro. 109 patients (mean age 66.7 yrs.) having at least 50% stenosis of the internal carotid artery or a cerebral ischaemia were studied. The haemodynamic effect of the stenosis on the entire anterior brain circulation supplied by the carotid artery was assessed. Stenoses were graded in 4 groups., Results: Significant VFR reduction occurred ipsilaterally in high grade (75-94%) stenosis and occlusion of the internal carotid artery, but not with moderate (50-74%) stenosis (p < 0.05). Ipsilaterally to stenoses there was a decrease in VFR, which was more marked in higher than in lower grade stenoses. Contralaterally there was an increase in VFR. These groups differed in a statistically significant way (p < 0.05)., Conclusion: This ultrasonic VFR method demonstrates the flow effect of carotid stenoses both ipsi- and contralaterally and adds to the understanding of the haemodynamics in individual patients.