M-mode and two-dimensional echocardiography (echo) were performed in 51 patients with pure or predominant mitral stenosis. Echocardiographic assessment of the severity of the stenosis was compared to the results of cardiac catheterization (cath); surgical evaluation of the mitral valve area was also obtained in 20 patients. M-mode is an excellent method for the diagnosis of mitral stenosis. However two-dimensional echo is much better for the assessment of its severity; in the present study correlations with cardiac catheterization have been excellent (r = 0.89, p less than 0.001). Major disagreement between echo and cath were found in 4 patients; 3 of them have been operated on and surgery has confirmed the echo results in all 3. Two-dimensional echo has also allowed correct prediction in the presence of mitral calcifications in 6 of the operated patients, whereas several false positive and negative diagnosis was made on M-mode. Two-dimensional echocardiography is therefore an excellent non-invasive technique for the diagnosis of mitral stenosis, measurement of mitral valve area and identification of mitral calcifications.