A retrospective clinical observation was made of 40 patients with postoperative cerebral dysfunction among 2634 patients who underwent open-heart operations in Severance Hospital. Yonsei University between 1962, the year the first successful open heart operation was done, and June 1985. Suspected causes of brain damage were reviewed. Brain CT findings were evaluated in 24 patients. There were 15 cerebral infarcts, 4 intracerebral bleedings, 3 ischemic brain damages, 1 infarction with intracerebral hemorrhage and 1 diffuse cortical atrophy from unknown cause. The most frequent site of cerebral infarction was the middle cerebral artery area with no predilection on the right of left.