Stroke is a significant cause of morbidity and mortality following coronary artery bypass grafting (CABG). Over a 30-month period, 245 consecutive patients undergoing elective CABG were prospectively examined to determine which risk factors might predispose to stroke following surgery. The risk factors evaluated included hypertension, diabetes, hypercholesterolemia, hypertriglyceridemia, smoking, atrial fibrillation, a history of cerebrovascular accident or transient ischemic attack, carotid artery stenosis > 60% documented by duplex scanning, severe atherosclerosis of the ascending aorta, and the presence of ventricular thrombus. Postoperative stroke occurred in five of the 245 patients (2%), four evident immediately on awakening and one on day 7 after surgery. The probable causes of the immediate strokes were atheroembolism in three patients and severe ipsilateral carotid stenosis in one. Hypertensive hemorrhage was responsible for the one case of delayed stroke. In this study, carotid artery stenosis did not presage stroke following CABG, but ventricular thrombus was highly predictive of stroke after surgery.