A case of the successful emergency surgery for the mitral prosthetic perivalvular leakage (PVL) which was diagnosed only by the transesophageal Doppler echocardiography (TEE) is reported. A 59-year-old male who had been diagnosed MS + TR + severe PH underwent mitral valve replacement with St. Jude medical valve 27 M. On the eighteenth postoperative day hemoglobinuria was noticed suddenly. Subsequently hemolysis and nonoriguric renal failure was aggravated, then we suspected PVL, but heart murmur was not audible or PVL could not been detected by the transthoracic echocardiography (TTE). PVL was detected for the first time by the TEE, then open heart resuture was emergently performed. The site of the PVL was the portion where the anterior mitral annulus adjoined the aortic annulus, that is, adjacent to the right fibrous trigone. This site is the portion which a surgeon should treat very carefully and where the PVL is very difficult to detect by the TTE. In regard to the detection of the PVL in mitral position, the TEE, which has ultrasonically no flow masking by the mitral prosthesis, is the very useful diagnostic means.