In 45 patients (pts.) with mitral stenosis (MS) multiple echocardiographic recordings of the posterior mitral leaflet (PML) were obtained and its motion pattern was carefully analyzed. 25 pts. showed only parallel motion (PM), one patient only opposite motion (OM) of the leaflets during diastole. In 19 pts. PM as well as OM (defined as backward movement of the PML immediately after the D-point and as forward motion during mitral closure, respectively) could be recorded at least two times. In most of these cases PM was impressive while OM could be demonstrated only by careful analysis of numerous recordings. In 4 of the 19 cases with PM and OM, however, the reverse was true. We conclude that OM should only be taken as evidence against MS when multiple recordings of the mitral leaflets have failed to reveal PM and when other echocardiographic signs of MS are missing. Possible explanations of the PM-OM combination are discussed.