Cardiogenic shock caused by papillary muscle rupture in acute myocardial infarction is potentially reversible by surgical treatment. A case of posterior myocardial infarction in a 79-year-old woman is reported. She was admitted to the hospital in cardiogenic shock. She had been suffered from chest pain for three days before admission. On physical examination diffuse rales and a grade 4/6 holosystolic apical murmur were present. The diagnosis of an acute posterior myocardial infarction was based on the electrocardiographic findings and serum creatine kinase level. Coronary angiography visualized subtotal occlusion of the left circumflex coronary artery. Transesophageal echocardiography demonstrated severe mitral regurgitation and the ruptured anterior papillary muscle connected to normal chordae tendineae and posterior mitral leaflet. In systole, the head of the ruptured papillary muscle moved like a whip in the left atrium. At operation, the ruptured papillary muscle was confirmed. Mitral valve replacement with a 27 mm St. Jude Medical prosthesis and coronary artery bypass grafting to the left circumflex coronary artery was performed. Postoperatively she was weaned intraaortic balloon pumping after 4 days and recovered uneventfully.