Background: Among the various techniques for the adequate exposure of the mitral valve, the extended transseptal approach is the essential prerequisite for accurate repair or replacement of the mitral apparatus. But the efficacy and safty of the extended transseptal approach has not determined in Korea yet. Materials and methods: Retrospective data of 80 consecutive patients, operated from September 1992 to July 1997 were reviewed. Seventy- eight patients underwent mitral valve replacement and 2 patients underwent excision of left atrial myxoma. Thirty-eight of 78 patients had other concomitant procedures such as aortic valve replacement(n=22), tricuspid annulopasty(n=14), coronary artery bypass graft(n=1) and closure of ventricular septal defect(n=1). Mean follow up was 23.3±15.0 months and total follow up was 1792 patient-months. Results: The hospital mortality rate was 3.8%(3 patients). Two deaths were due to low cardiac output and one due to postoperative bleeding of coagulopathy. Among the 46 patients who had atrial fibrillation preoperatively, 45 had atrial fibrillation postoperatively and 1 converted to sinus rhythm. All 34 patients who were in normal sinus rhythm preoperatively remained in sinus rhythm after the operation. Mean aortic cross clamping time was 62 minutes for isolated mitral procedure and 90 minutes for concomitant procedures. There were no specific complications related to this approach. Conclusions: We suggest that the extended transseptal approach is an easy and good method for mitral valve surgery, especially in patients with small sized left atrium.