A new technique of left atrial plication (LAP) for giant left atrium (GLA) resulting from mitral regurgitation (MR) is reported. A 66-year-old man was found to have NYHA class III resulting from severe MR, mild TR and GLA with a left atrial diameter (LAD) of 107mm on echocardiogram. Chest X-ray showed the cardiothoracic ratio (CTR) to be 92%, and the right side CTR was 88.4%. Surgery was performed under general anesthesia with endotracheal intubation. Under cardiac arrest established by antegrade and retrograde cardioplegia, mitral repair was performed first through a superior transseptal approach. Left atrial resection was continued paralell to the mitral posterior annulus and to the right side wall of the left atrium, following the right side resection. Simultaneously the left atrial wall was incised 3 to 4cm in width all the way along the resection line and it was closed by a running suture of 3-0 prolene. The continuous line of the left atrial plication formed a spiral shape. A prominent portion of the atrial septum resulted from the LAP and the right atrial wall was also resected and plicated. The postoperative course was uneventful, and the postoperative CTR reduced to 71% with a right side CTR of 54.4% with reduction of LAD to 67mm on ultrasound cardiogram (UCG). This spiral LAP was considered more effective to reduce all dimensions of the giant left atrium dilated in all directions in comparison with other LAP methods previously reported.