A study of seventy-five cardiac patients, including periodic medical, psychiatric, neurologic and psychologic examinations, was made, with a four-year follow up. A preoperative history of cerebral vascular accidents was elicited in five (8.9 per cent) of the fifty-six patients with rheumatic heart disease. Thirty-three of these patients underwent mitral commissurotomy. In the period immediately after commissurotomy, cerebral vascular complications (strokes) developed in three (9.1 per cent) patients. Thus, the incidence of known cerebrovascular complications rises to 18 per cent in the patients with rheumatic heart disease undergoing mitral surgery. Consequently, almost one in five such patients may suffer cerebral involvement, in either the pre- or immediate postoperative period. Detailed examinations were made preoperatively, and repeated postoperatively at three weeks, six months and yearly, up to four years. Psychologic tests included measures of intelligence, organic involvement of the brain and projective technics. Psychiatric history, mental status and neurologic examinations were also repeated periodically. Medical follow-ups included recatheterization studies and exercise tests. The psychiatric and psychologic evaluations prior to cerebral vascular accidents revealed that these patients were adjusting in a manner in keeping with their cardiac illness. Neurologic examination at that time revealed no major signs of central nervous system deficit in the three patients in whom cerebral complications developed following commissurotomy. In two patients undergoing commissurotomy evidence of serious neurologic involvement developed within the first two days, and in the third patient on the twelfth postoperative day. While the immediate impact of these complications resulted in pronounced neurologic deficits, follow-up studies showed gradual recovery. Of two patients with initial expressive aphasia, one retained only a mild paresis of the left arm, while the other showed some degree of residual expressive aphasia, even after three and a half years. The third patient, with initial hemiplegia, achieved almost complete recovery. The psychologic retests indicated definite impairment associated with the occurrence of cerebral vascular accidents and a gradual recovery of psychologic functioning to the pre-operative level, with minor residuals remaining in perceptual motor abilities and personality functioning after three years. Intelligence, as measured by the Wechsler-Bellevue test, indicated almost complete return to the preoperative level within two years. Psychiatrically, two of three patients with postoperative neurologic deficit made satisfactory readjustments and returned to previous occupations; while the third (with residual aphasia) had definite rehabilitation difficulties and could not return to her full-time professional job. Improvement in cardiac dynamics following the surgery was uniformly disappointing in these three cases. Among many factors influencing readjustment, outstanding was availability of supportive individuals in the patient's milieu and his ability to utilize them in his day-to-day rehabilitative efforts.