The interrelationship between postoperative psychosis, neurologic symptoms, and changes in tests of cognitive performance have been studied in a series of 60 cardiac valvular patients who underwent open heart surgery. The effects of preoperative psychological, psychiatric, and cardiologic factors on postoperative cognitive changes were analyzed. The investigation period was from five months before up to five months after the operation. There was a general trend towards improvement in intellectual performances. The psychotic group, however, still showed a persisting impairment in some visual and psychomotor tests several months after the surgery. The group with neurologic symptoms showed impairment in one visual test. Of the preoperative variables, mitral valve disease, a high level of hypochondriasis and anxiety, and poor performance in some visual and psychomotor tests predicted postoperative intellectual impairment. The results suggest two types of cerebral complications of open heart surgery. Postoperative psychosis reflects diffuse brain dysfunction manifesting itself in psychological tests long after the clinical symptoms have resolved. The presence of neurologic symptoms refers to a focal or lateralized injury. Both the neurologic and neuropsychologic findings indicate that the right hemisphere may be prone to dysfunction than the left hemisphere.