A patient with mitral insufficiency is described who developed severe hemolytic anemia six months after mitral valvuloplasty. Various laboratory tests suggested that the cause of the hemolysis was mechanical. A second heart operation was therefore performed which revealed intact valve function. With respect to the mechanical cause of hemolysis a bioprosthesis was implanted, but the patient died shortly after this operation. Since similar cases are not reported in the literature the authors invite for discussion of this case.