Thirty-two patients with mitral regurgitation secondary to ruptured chordae tendineae were studied by cross-sectional echocardiography. Twenty of them subsequently underwent operation. Three signs are described. (1) Non-coaptation of the leaflets (55%). (2) Systolic fluttering echo in the left atrium originating from the mitral valve (20%). (3) A previously not described small diastolic chaotically moving echo in the short axis section of the left ventricle at the level of the papillary muscles (65%). The combined sensitivity of these three signs was 85%. The specificity of the three signs when compared with those of 107 patients with mitral regurgitation of different aetiologies studied by cross-sectional echocardiography was 99%, 100% and 99%, respectively. Six patients were studied after mitral valve repair; restriction of the surgical treated leaflet and reduction of its valve area was seen in all of them, and the disappearance of the valvar signs of ruptured chordae noted. The persistence of the small echo sign in the short axis of the left ventricle indicated its chordal origin.