The twenty patients in this study were selected from a group in whom valvulotomy was performed for mitral stenosis at the University Hospital, and Veterans Administration Hospital, Birmingham, Alabama. These patients were chosen because kinetocardiographic records were obtained before and after the operation. The majority of patients in the group have been followed up for approximately two years after mitral surgery. In addition, several patients were included because of their unusual clinical and kinetocardiographic findings, although the follow-up period has not been as long. Table I represents the classification of the various patients into special groups to facilitate subsequent discussion. As this is a small and select series, analysis of the clinical features will not be undertaken, and only the data relevant to the interpretation of the kinetocardiograms are presented in Table I. The functional class of patients, as listed, is based upon that of the American Heart Association, and the presence of right-sided congestive heart failure is noted in each instance (indicated by the presence of pedal edema, enlarged liver, and an elevation in venous pressure). It is obvious from Table I that many of the patients in all groups were of the same functional class before surgery for mitral stenosis, while the results following the procedure varied considerably. TECHNICS