Left ventricular geometry and function were assessed in 20 patients with mitral stenosis (MS) and in another 20 patients with mitral insufficiency (MI) five days before and 12 days after mitral valve replacement by transthoracic (TTE) and transesophageal (TEE) echocardiography, as well as late postoperatively (mean: 194 days) by TTE. The continuity of the subvalvular apparatus could not be preserved in any of these patients. In mitral stenosis the area ejection fraction (AEF) in the short axis of the left ventricle (LV) did not change significantly early or late postoperatively. There was a significant lengthening of the left ventricular longitudinal axis in the apical four chamber view whereas the transverse axis remained unchanged. This was likely the result of the discontinuity between the mitral valve and the papillary muscles. AEF and ejection fraction (EF) determined in the four chamber view showed a slight tendency to decrease in the postoperative phase. Patients with mitral insufficiency likewise showed a significant increase of the LV longitudinal diameter postoperatively. In the short axis of the left ventricle and in the apical four chamber view a significant reduction of the AEF was observed. Furthermore, left ventricular EF dropped significantly postoperatively. This decrease was caused by the extension of the LV longitudinal axis accompanied by an enlargement of the transverse diameter as well as by an afterload increase, and a masked impairment of left ventricular function preoperatively. Wall motion analysis of the LV in both groups documented new postoperative hypokinesis especially in the septal segments. At late postoperative examination the hypokinesis disappeared in about 50% of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)