Percutaneous balloon mitral valvotomy (PBMV) compares well with surgical commissurotomy, showing comparable improvement in symptoms and catheterization-proven valve area early after the procedure. This study reports the New York Heart Association class, mitral valve area calculated by echocardiography, and the results of transseptal cardiac catheterization 2 years after PBMV. The data are compared with the status immediately before and after PBMV. Forty-one patients returned to enter the study (mean follow-up time 24 +/- 3 months). All patients were evaluated clinically by the same investigator who had seen them at the time of PBMV. Transseptal cardiac catheterization and echocardiographic analysis (2-dimensional and Doppler echocardiography) were performed on the same day. At follow-up, 17 patients were class I, 20 were class II, and 4 were class III. Although the mitral valve area calculated by cardiac catheterization increased significantly from immediately before to immediately after PBMV there was a decrease in the calculated mitral valve area at 2-year follow-up. Echocardiographic analysis did not show as large an increase in mitral area, immediately after PBMV, and no significant decrease in mitral valve area at 2 years (before PBMV planimetry 1.1 +/- 0.1 cm2; immediately after 1.8 +/- 0.1 [p less than 0.05]; follow-up 1.6 +/- 0.1 [p = not significant compared with immediately after PBMV]). Doppler halftime measurements were similar. PBMV is effective therapy with good midterm results for selected patients with mitral stenosis.