Nonpulsatile perfusion techniques with extracorporeal circulation for open-heart surgery and aortocoronary bypass grafting are widely used; this treatment is often followed by temporary or permanent neurological deficits. Experimental studies suggest that pulsatile flow may be of greater benefit because of its ability to ameliorate cerebral microcirculation. We therefore investigated 22 men who underwent aortocoronary bypass grafting. Patients were randomly divided into either a group undergoing nonpulsatile (n = 14) or pulsatile flow (n = 8). Neurological examinations were done prior to the operation and on the 7th postoperative day. EEG, cerebral blood flow (CBF), and the metabolic rates of O2 (CMR O2) and glucose (CMR Glucose) were measured before anaesthesia and 30 minutes after the start of extracorporeal circulation, when venous blood temperature was 26 degrees C. Postoperative neurological symptoms consisted of cranial nerve palsies, dysfunctions of the visual cortex, cerebellar symptoms, and slight arm paresis, but no differences between the two treatment groups were detected. Moreover, changes in EEG, CBF, and CMR rates during anaesthesia did not differ between the two groups. Our data suggest that pulsatile flow is not superior to the nonpulsatile perfusion technique, but to confirm this larger patient samples are required.