A conventional reoperation via full sternotomy approach is associated with a higher risk of heart injury compared with first time operations. We employ a minimally invasive cardiac surgery (MICS) for valve reoperations in order to minimize dissection of sternal adhesions. We evaluated MICS for mitral reoperation in this report. We retrospectively analyzed 20 patients (group P) who underwent mitral reoperation via partial lower hemisternotomy (PLH) from July 1997 through March 2002, and 13 patients (group F) who underwent mitral reoperation via full sternotomy from April 1990 through June 1997. All patients received mitral valve replacement in both groups. Concomitant Maze procedures were significantly more frequent in group P (group P: n=8, group F: n=1). Aortic cross clamp times were significantly longer in group P (group P: 110±5min, group F:87±11min). The blood loss during operations was significantly less in group P (group P: 666±100ml, group F: 2, 405±947ml). Postoperative ventilation time and the length of intensive care unit stay were significantly shorter in group P. In group P and F the occurrence of a heart injury associated with sternotomy was 0/20 (0%), 2/13 (15%) respectively. Hospital mortality was 0/20 (0%), 2/13 (15%) respectively. There were neither any hospital deaths nor any postoperative major complications in group P. We conclude that PLH for mitral reoperations could be performed safely and is an alternative approach for mitral reoperations.