Twenty-four patients subjected to mitral commissurotomy were investigated by means of psychiatric interviews, the House-Tree-Person Drawing Test, and the Inside-of-the-Body-Test. The findings obtained through the drawing tests presented few significant departures from those noted previously on random surgical subjects. Evidence of severe anxiety and various psychological defenses in response to the surgical experience, as well as manifestations of long-term characterological and neurotic problems were noted. In addition, the drawings provided clues to fantasies concerning the prospect of repair of a long-standing organic defect. The presentation of detailed case reports serves to underscore the intimate interweaving of psychological and somatic phenomenology in patients with chronic heart disease. Examples are furnished illustrating the precipitation of congestive failure and other cardiac symptomatology by psychological factors, and it is pointed out that cardiorespiratory symptoms occurring in patients with known mitral stenosis need not necessarily be cardiogenic. Moreover, a psychic stimulus that at one time evokes anxiety may be followed at some later date by cardiac symptomatology. The realistic importance of the heart as well as its protean symbolic meanings as suggested by the specificity of Inside-of-the-Body drawings and case histories lends distinctive qualities to cardiac surgery. In addition, the incorporation of the chronically diseased or defective heart into the personality structure and history of the subject leads to complex, unpredictable, and often contradictory attitudes toward its repair, as well as to the well-known discrepancies between the anatomical and functional consequences of commissurotomy. Among the major psychiatric reactions noted in this study was a postoperative condition here termed the catastrophe reaction, resembling the early reactions of victims of acute poliomyelitis, and ascribed in part to the use of light narcosis and a motor paralyzant, succinylcholine, during the operation. It is suggested that the relative infrequency of prolonged postoperative psychotic reactions may be attributable in part to an unintended prophylactic psychotherapy occasioned by this study. The implications of this are followed in stressing the important therapeutic potential in the surgeon's relationship with the patient. Tell me where is fancy bred, Or in the heart or in the head?