Long-term follow-up after percutaneous transvenous mitral commissurotomy (PTMC) is limited. Ninety-four middle-aged (51±9 years) mitral stenosis patients who underwent successful PTMC were followed up with annual echocardigraphy for 6.1±1.4 years. PTMC success was defined as either mitral valve area (MVA) >1.5 cm² or a MVA of more than twice the pre-procedural value, together with no worsening of mitral regurgitation >grade 2+. Mitral valve replacement (MVR), worsening of congestive heart failure (CHF), and thromboembolism were sought for survival analysis. Restenosis was defined as loss of more than 50% of the initial procedural MVA gain. Functional limit of daily activities was assessed through a questionnaire. The study population was divided into group 1 (post-procedural MVA >2.0 cm²), group 2 (MVA >1.5 cm² and ≤2.0 cm ²) and group 3 (MVA ≤1.5 cm²). The 6-year survival with freedom from MVR, CHF, thromboembolism, and combined events (MVR + CHF) was 92%, 95%, 91%, and 88%, respectively. No group 1 patient experienced MVR or CHF. Restenosis was predominant in group 3. Deterioration of daily activities during follow-up was not observed in group 1; however, it was significant in group 2 (p<0.05) and group 3 (p<0.001). These results demonstrated that patients who attained a large MVA (>2.0 cm²) immediately after PTMC maintained their procedural benefit with less clinical complication and with less limitation of daily activity. (Jpn Circ J 1999; 63: 597 - 604)