Echocardiographic studies of the mitral valve were performed in 57 patients with pure or predominant mitral stenosis who subsequently underwent surgery (30 commissurotomy, 27 valve replacement). Mitral valve calcification was graded heavy (thick, conglomerate echoes), light (multiple, discrete linear echoes) or none (thin, or duplicate signals). Valve mobility, measured as the excursion from the systolic closed position to the fully opened position in diastole, was classified as normal (20 mm or over), restricted (16-19 mm) or poor (15 mm or less). Absence of mitral valve calcification was the most useful echocardiographic indicator for commissurotomy (18 of 19 cases). The most reliable criteria for valve replacement were heavy valve calcification (11 of 11 cases) and poor cusp mobility (11 of 11 cases). The poor mobility group included 3 patients with heavy calcified valves. Thus 37 of 57 cases (65%) could be reliably categorized regarding the type of surgery performed using these 3 parameters. The remaining echocardiographic parameters (normal mobility, restricted mobility and light calcification) were less valuable in the assignment of the operative category. Echocardiographic assessment of mitral valve calcification and mobility appears to be of value in planning the surgical approach in patients with pure or predominant mitral stenosis.