A 78-year-old woman, after mitral valve repair by placement of No. 29 Duran annuloplasty ring 6 years previously at another hospital, was admitted because of chronic heart failure and hemolytic anemia. A Doppler echocardiogram showed that mitral regurgitation was still present but not severe. The diagnosis of hemolysis was made by decreased serum haptoglobin, elevated serum lactate dehydrogenase (LDH) and progressive anemia. We estimated that the mechanism of hemolysis was related to the mitral annuloplasty with a ring and improvement of symptoms would be impossible without removal of the ring. On 25 June, 2001, the reoperation was performed through a median sternotomy, but adhesion was so severe that a standard left atriotomy was impossible. Therefore, the right thoracic cavity was opened through a mediastinal pleurotomy and a transseptal approach was taken through right atriotomy. The annuloplasty ring was partially detached from the mitral valve ring, and that part was non-endothelialized. We concluded that an eccentric regurgitant blood stream directed to the non-endothelialized portion of the annuloplasty ring appeared responsible for the hemolysis. The ring was removed and mitral valve replacement was performed with a 25mm Carpentier Edwards bioprosthesis. The removal of the source of hemolysis and the mitral valve replacement allowed prompt recovery from severe hemolysis. Decreased serum haptoglobin, elevated LDH and progressive anemia recovered postoperatively. The reoperation used was safe and effective in relieving hemolysis. The scanty literature concerned was reviewed.