In 20 patients (6 male; age 56.5+/-6.4 years; BSA 1.6+/-0.1 m(2)) undergoing port-access mitral valve surgery, automated intraoperative transcranial Doppler was used to monitor absolute amount, side distribution, and type of embolic events during selected phases of the procedure to evaluate the impact of specific surgical manoeuvres on cerebral microembolism. The rate of events per minute was acquired for the following five operative periods: from cardiopulmonary bypass (CPB) set-up to CPB start, from CPB start to aortic clamping, first minute after aortic endoclamp inflation, first minute after aortic endoclamp deflation, and first ten minutes from CPB weaning start. Endoclamp navigation into the aortic arch, CPB start and CPB weaning determined the highest absolute count of embolic events. When embolic rate was normalised for length of selected operation periods CPB start (1.58+/-1.9 events/min), endoclamp inflation (1.42+/-1.7 events/min) and endoclamp deflation (3.1+/-3.5 events/min), resulted as the most critical phases. No side prevalence was observed. In conclusion, brain embolism during port-access mitral valve procedures occurs predominantly at CPB start and during ascending aorta clamping and unclamping. Aortic arch navigation with catheters exposes to the risk of cerebral embolic events.