The 37-year-old woman underwent mitral valve replacement (MVR) with a Carpentier-Edwards bioprosthesis for hypertrophic obstructive cardiomyopathy (HOCM) 14 years previously. Since the 10th postoperative year, progressive right heart failure due to tricuspid valve regurgitation was recognized. Therefore, reoperation was recommended. At the time of reoperation in the 14th postoperative year, the cavity of the left ventricle was markedly diminished. In particular, deformitiy of the right ventricle was found. This was considered to be the effect of progressive septal hypertrophy. The mitral valve was replaced with a 25mm Carpentier-Edwards and the tricuspid valve with a 31mm Carpentier-Edwards bioprosthesis. Although the weaning from the cardiopulmonary bypass was uneventful, postoperative right heart failure occured with hyperbilirubinemia followed by multiple organ failure. She died on the 47th postoperative day. At autopsy, the intraventricular septal thickness was 24mm and the cavities of left and right ventricle were almost occluded by septal hypertrophy. This is considered to be a rare case of long-term survival after MVR in a patient with HOCM.