The field of cardiac surgery is rapidly enlarging. Including as it does the treatment of wounds of the heart and acute infections of the pericardium, the Brauer operation, the various recent procedures advocated for angina pectoris, and, finally, the subject of valvular stenosis, it bids fair to claim increasingly more attention at the hands of the surgeons. Some day perhaps there will be an association for cardiac surgeons, but until specialism is thus limited the American Association for Thoracic Surgery will remain the Mecca for all surgeons interested in various forms of cardiac surgery. We have little clinical experience to add to that already published,1 but there have been certain experimental advances that lead us to hope that the two patients now ready for operation will give us more satisfactory results. RATIONALE OF THE PROCEDURE Any discussion of the possibilities of surgery in the treatment of mitral stenosis involves