We evaluated the role of intraoperative transcranial Doppler sonography in improvement of carotid endarterectomy results. We analyzed the outcome of 38 carotid endarterectomies (CEA) performed in 22 female and 16 male patients with symptomatic carotid stenosis, aged between 43 and 78 years (av. 61.8 years). Constant measurements of peak and average velocity (Va) were taken during following stages of CEA:-after anaesthesia--during 120 s crossclamp test, -after shunt insertion (5 patients),-immediately after and 5 min after crossclamp release. RESULTS We obtained following values of Va in particular stages of CEA:-after anaesthesia 0.54 m/s (0.38-1.08),-during 120 s crossclamp test 0.25 m/s (0.12-0.58),-after shunt insertion 0.47 m/s (0.32-0.78),-immediately after crossclamping 0.72 m/s (0.51-1.40),-5 min. after crossclamp release 0.62 m/s (0.42-1.27). In 2 cases no blood flow velocity increase was found after shunt insertion. The immediate correction of shunt positioning was done. In 2 other patients no hemodynamic effect after CEA was detected (no blood flow velocity increase in MCA and at the same time, no neurological impairments were noticed). After quick investigation inferior carotid artery kinking above the arteriotomy site and its stenosis after suturing were found. Both of these abnormalities were removed and since that moment the blood flow velocity in MCA increased, in comparison with preoperative values. CONCLUSIONS intraoperative transcranial doppler monitoring 1) allows to identify any kind of blood flow disturbance in MCA during each stage of CEA which appears before neurological impairment, 2) gives the possibility of shunt functioning evaluation, 3) enables to avoid intraoperatively unpredictable situations that may result in imminent cerebral ischemia, 4) 70% decrease of blood flow velocity in MCA is the indication for shunt insertion, 5) proved to be very helpful in (in 10% of our material) improving the results of all carotid endarterectomies.