A 51-year-old male was admitted to our Institution with a complaint of dyspnea on effort. He had undergone coronary artery bypass grafting and mitral valve annuloplasty three years previously. The left ventriculograms showed severe mitral regurgitation. The coronary angiograms revealed an ITA graft and two SVG grafts were fully functioning. Considering the risk of injury of ITA/SVG graft during redo median sternotomy, we approached the heart through right anterolateral thoracotomy. Mitral valve replacement was performed under profound hypothermia without aortic cross clamping. Temporary reduction of perfusion flow was useful in order to obtain a better visual field. His postoperative course was uneventful. Right thoracotomy has an advantage over median sternotomy when reoperation is to be done for patients with a functioning ITA graft.