Stroke is one of the most devastating complications following coronary artery bypass grafting (CABG) with an overall incidence ranging from 2.0 % to 3.2 %. The presumed etiology for the majority of strokes after CABG is atheroembolism from the diseased aorta ascendens caused by surgical manipulation. Off-pump coronary artery bypass grafting (OPCAB) allows the construction of bypass grafts without surgical manipulation of the aorta. Yet a trial comparing different surgical strategies with stroke as the primary end point would require several thousand patients to achieve an adequate statistical power. The number of patients can be substantially reduced, if cerebral damage is assessed by diffusion-weighted magnetic resonance imaging (DW-MRI). Using DW-MRI we have recently demonstrated that 25% of a patient population undergoing CABG without an increased risk of stroke showed new cerebral infarctions. These new cerebral lesions all showed an embolic pattern, became visible at T2-weighted images and were clinically silent, e .g. did not cause a new focal neurologic deficit. Given the much higher frequency of cerebral lesions assessed by DW-MRI than clinically apparent stroke, DW-MRI is an ideal surrogate parameter for the assessment of cerebral damage in patients undergoing CABG.