A 69-year-old man developed a rupture of the papillary muscle on the fifth day of acute posterior myocardial infarction. The two-dimensional echocardiographic features of ruptured papillary muscle included (1) mobile mass of echos attached to normal chordae tendineae in the left ventricle, (2) absent tip of papillary muscle, and (3) mitral valve prolapse. Noninvasive, two-dimensional echocardiography can reveal correct diagnosis of ruptured papillary muscle suspected clinically.