Percutaneous balloon mitral commissurotomy was attempted in Tunisia, where rheumatic fever is still endemic, in 463 consecutive patients with severe rheumatic mitral valve stenosis. Their mean age +/- SD was 33 +/- 12 years (range 8 to 68), 324 patients (70%) were women, and 327 (71%) were in sinus rhythm. Valvotomy was technically successful in 454 patients (98%). The mean mitral valve gradient decreased from 20 +/- 7 to 6 +/- 4 mm Hg, mean left atrial pressure decreased from 27 +/- 8 to 15 +/- 6 mm Hg, cardiac index increased from 3.0 +/- 0.7 to 3.6 +/- 0.8 L/min/m2, and Gorlin mitral valve area, from 0.97 +/- 0.19 to 2.2 +/- 0.4 cm2 (all p < 0.001). Two-dimensional echocardiographic mitral valve area increased from 1.03 +/- 0.18 to 2.15 +/- 0.36 cm2 (p < 0.00001). A final valve area of > or = 1.5 cm2 was achieved in 98% of patients. Multivariate analysis identified a pre-mitral valve area < 0.8 cm2 and an echocardiographic score (echo score) > or = 12 as the strongest predictors of residual stenosis (final mitral valve area < 1.5 cm2). Major procedural complications included mortality (0.4%), tamponade (0.7%), thromboembolism (2.0%), severe mitral regurgitation (4.6%), significant (pulmonary to systemic flow ratio > or = 1.5) interatrial shunt (4.8%). Four hundred thirty patients were followed up between 6 and 82 months (mean 37 +/- 22): 95% were in functional class I to II without reintervention, and 7 patients died (1.6%); restenosis (echocardiographic mitral valve area < 1.5 cm2) occurred in 10.4% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)