An unusual but often lethal complication of mitral valve replacement is rupture of the left ventricle. From March 1977 through June 1990, 424 mitral valve replacements were performed as isolated or combined procedures. Rupture of the posterior wall of the left ventricle was observed in 3 patients. Their was one type I and two type II rupture. Once the diagnosis was made, all of the patient were connected to the heart-lung machine again and total cardiopulmonary bypass is re-established. Repair was attempted in all of them from the outside of the heart. One of them was successively repaired but two were failed due to myocardial ischemia by circumflex coronary artery injury and failure of adequate closure of the ruptured site. From this results, we concluded that prevention is the best solution. But if we encountered this condition, early diagnosis and rapid treatment may improve the patient`s chances for survival.