Any one of a number of psychologic patterns may appear cardiotomy: (1) Some patients may be elated and confident after awakening from anesthesis and have no severe changes of affect or neurologic deficit. Denial seems to be for them an adequate defense against anxiety. (2) Others are disoriented and manifest neurologic disturbance immediately after awakening, without a lucid interval. The sensorium begins to clear five days after surgery. (3) Some patients go into delirium after being lucid for as long as a week and have hallucinations, illusions, and motor excitation for a few days-or over several weeks. Pathologic brain changes that are apparently anatomical correlates of neurologic deficits in delirium include anoxic lesions of the hippocampus, and infarcted foci. Physiologic factors that contribute to this reaction include: long periods of extracorporeal circulation, arterial hypotension during surgery, emboli, and low postoperative cardiac output. Age, and the type and severity of heart impairment are also factors. Psychologic factors to be taken into account include preexisting psychopathology and the failure of denial under the stress of physical symptoms or hospitalization. Delirium is fostered by sensory overload (or deprivation) in the recovery room and intensive care unit, and by staff tension. Modification of the intensive care unit environment, the administration of antipsychotic drugs, and metabolic correctives are recommended. Preoperative psychologic evaluation, with therapy as needed, preliminary familiarization with perioperative procedures, as well as collaboration between psychiatrist and surgeon, can do much to prevent post-cardiotomy delirium.