Background: Comparison of neurological parameters in patients undergoing prosthetic heart valve replacement with two operating techniques-either cardioplegic arrest of the heart under hypothermic cardiopulmonary bypass (CPB) or the heart beating on normothermic bypass, with or without cross-clamping the aorta, without cardioplegic arrest. Methods: Fifty valvular surgery patients were randomly assigned into three groups. Sixteen patients underwent beating heart valve replacement with normothermic bypass without cross-clamping the aorta, 17 patients underwent the same procedure with cross-clamping the aorta and retrograde coronary sinus perfusion, and the remaining 17 patients had conventional surgery with hypothermic bypass and cardioplegic arrest. Results: Two-channel electroencephalography (EEG) was recorded to assess changes in cerebral cortical synaptic activity and 95% spectral edge frequency values were recorded continuously. Bispectral monitoring was used to measure the depth of anesthesia. Blood flow rates in middle cerebral artery (MCA) were measured by transcranial Doppler (TCD). Reduction in spectral edge frequency (> 50%) or bispectral index (BIS) (< 20) or transcranial Doppler flow velocity (> 50%) was detected in four patients in Group 1, five patients in Group 2, and three patients in Group 3. BIS or EEG values never reached zero, which indicates isoelectric silence during surgery. Gross neurological examinations were normal in all patients postoperatively. Conclusion: There is no difference regarding neurological monitoring results between on-pump beating heart and hypothermic arrested heart valve replacement surgery. Also no significant difference was encountered among the groups regarding the clinical outcomes.