To assess left ventricular shape and contraction pattern under the condition of the narrowed mitral orifice, 41 patients with mitral stenosis were studied by cross-sectional and M-mode echocardiography. Abnormal left ventricular configuration and asynergy were observed in 23 patients (56%). The change in configuration persisted during the cardiac cycle and was mainly due to a straightening and abnormal motion of the interventricular septum. Furthermore, hypokinesis or akinesis of the posterior left ventricular wall contributed to the change of left ventricular shape. Consequently the left ventricular shape became from circular to half moon- or pear-like configuration. Of these 23 patients, 19 had a severe degree of subvalvular lesion, whereas such a lesion was noted in only 6 of the 18 patients with normal left ventricular shape and contraction pattern. It is considered that a rigid mitral complex immobilizes the posterior wall of the left ventricle in patients with mitral stenosis. In addition, tricuspid regurgitation, which was frequently observed in our patients, may play an important role in abnormal septal motion. This study showed that abnormal left ventricular shape and asynergy in the posterior wall are not rare in patients with mitral stenosis and are due to a rigid mitral complex and associated tricuspid regurgitation.