Neurological dysfunction following cardiac surgical procedures is now well recognized. In order to minimise this serious complication, we instituted various protocols related to the potential causes of perioperative stroke such as: (1) components and use of the heart-lung machine; (2) air embolization; (3) intrinsic cerebro-vascular disease; (4) atheroemboli from the ascending aorta and (5) clot emboli from the left ventricle. We employed certain methods of operation of the heart-lung machine, air evacuation manoeuvres and a pharmacological brain protection protocol. These protocols were applied in a series of 1487 consecutive cardiac surgical procedures performed between 1984 and 1989; 127 patients died (8.54% mortality) and 16 patients (1.08%) suffered major neurological syndromes. Among the latter patients, 4 distinct groups were identified. Group A consisted of 6 patients who remained unresponsive after operation. In group B were 6 patients who awakened after operation but had clinical evidence of focal cerebral infarction. Group C included 3 patients who were initially intact neurologically but in whom neurological deficits developed later. Group D contained 1 patient who had severe mental aberration but no focal neurological deficits. Causative factors, including atheromatous embolism, perioperative hypotension and air embolism, were suspected in 12 of these 16 patients (75%) in groups A, B and C. The outcome was poor for unresponsive patients and 9 out of the 16 died or remained comatose (56.6%).