The authors analyzed a group of 50 patients with an implanted artificial mitral valve. Group I consisted of 20 patients with an isolated left venous ostial stenosis. Group II consisted of 23 patients with a complex mitral disease, and group III--of 7 patients with mitral incompetence. Depending on the degree of improvement, the first two groups were divided into two subgroups: group Ia (13 patients) and group IIa (15 patients) with full clinical improvement, and group Ib (7 patients) and group IIb (8 patients) still requiring cardiological drugs and from time to time--dehydrating drugs. The observation time was from 1.5 to 4 years (on the average 39 months). In all the patients the artificial valve functioned properly. Before and after surgery the clinical state was evaluated according to NYHA, heart volume index (WOS), cardiopulmonary index (WSP) by a radiological examination, left-ventricular diastolic dimension (WRLK), left-ventricular systolic dimension (WSLK), left-ventricular end-diastolic volume index (WOKRLK), left-ventricular end-systolic volume index (WOKSLK), right-ventricular diastolic dimension (WRPK) and left atrium were evaluated by means of echocardiographic examination. Before surgery all the patients underwent the measurements of pressures in the pulmonary circulation, pulmonary resistance and heart index. The authors found a correlation between a degree of improvement after surgery and a functional group before surgery. Eleven patients from functional group III according to NYHA had been (before surgery) in a state of advanced circulatory failure (IV functional group). Clinical improvement was confirmed by statistically significant decrease in heart dimension evaluated by radiological and echocardiographic examinations. In group I left atrium dimension (LP) was significantly statistically larger in patients with incomplete clinical improvement. The authors also found a dependence of a distant result on a degree of hypertension in pulmonary artery, increased pulmonary resistance and decrease in stroke volume.