Improving intraoperative and postoperative myocardial protection and better construction and design of valvular prosthesis has reduced the mortality of MVR. But, ventricular rupture after MVR occurred occasionally and represented a potentially lethal complication. Transverse midventricular disruption presented as refractory myocardial failure immediately on termination of bypass or later often on initial period of good hemadynamics. From Jan., 1985 through Dec., 1991 131 MVRs were performed as isolated or combined procedures. Rupture of the posterior wall of left ventricle was observed in 2 patients. There were 2 type III ruptures Prevention is of utmost importance, and by taking certain precautions, the chance of ventricular rupture can be reduced. Repair should always be done by patch technique in the aid of the use of cardiopulmonary bypass with cardioplegic arrest. When the laceration is in the middle of the posterior left ventricle, external repair with the pericardial patch can be attempted first.