Two-dimensional echocardiograms were correlated with the operative findings and surgical procedures in 46 patients with mitral stenosis. In addition, a new projection evaluating subvalvular lesion more precisely was reported. Two-dimensional echocardiographic findings studied were 1) pathology of the two leaflets of the mitral valve, 2) valve area, and 3) subvalvular lesion. The findings of leaflets and valve area were well correlated with the operative findings. But there were six cases with discrepancies in the initial 22 cases about the findings of subvalvular lesion; there were 5 false negative and one false positive case. It was considered that insufficient information about the appositional zone of the mitral valve and chordae tendineae made it difficult to evaluate them correctly. We have designed a new projection for delineating the subvalvular apparatus and employed in the next 24 cases, and the transducer was placed near the apical heart to visualize 4 chambers. This eliminated greatly the false positive cases (only 2 out of 24 cases). There were three cases of mitral valve replacement (MVR) in the initial 22 cases, but we could expect the necessity of MVR in only one case, and we had to perform chordotomy, papillotomy, or debridement as well as commissurotomy in two false positive cases. In the next 24 cases, however, we could predict it in all three cases of MVR before the operation. It was valuable for surgery of mitral stenosis to get enough information about the subvalvular lesion as well as mitral leaflets by two-dimensional echocardiography.