This report is a clinical study of 23 patients undergoing open heart surgery and how some responded to it. It is evident that these patients reacted to the operation as presenting not merely a symbolic but realistic threat to life. The presence of anxiety and the use of denial preoperatively are described. Two cases of postoperative "cardiac psychosis" are reported and their relationship to the "catastrophe reaction" and "post-cardiotomy delirium" commented upon. The intensive care unit is seen as a life-saving necessity in modern heart surgery but at the same time frequently perceived by the patient as psychologically threatening. Certain prophylactic psychological measures are discussed.Abstract Teaser