Mitral valve perforation is a rare cause of severe mitral regurgitation, which occurs most commonly as a secondary involvement of aortic valve endocarditis. The probable mechanisrns are direct extension of the infection from the aortic valve, infected aortic regurgitant jet striking the ventricular surfaces of the mitral-aortic intervalvular fibrosa(MAIVF) and the anterior mitral leaflet(AML). Early recognition of these subaortic complications in patients with aortic valve endocarditis is important because (1) these complications may produce severe mitral regurgitation and hemodynamic collapse, (2) the presence of severe mitral valve involvement may present as primary mitral valve disease, (3) these complications can be overlooked during aortic valve replacement, and (4) cause difficulty in valve replacement and high mortality. We report two cases of AML perforation observed in patients with bicuspid aortic valve endocarditis.