Aims To assess long-term outcome in a typical Western population of predominantly unfavourable patients undergoing Inoue balloon mitral valvuloplasty. Outcome amongst patients has only been undertaken in the medium term. Long-term echocardiographic data in particular are scarce. Methods Inoue mitral valvuloplasty was attempted in 106 patients. There were six technical failures; the procedure was therefore completed in 100 patients, who underwent annual clinical and echocardiographic follow-up. Results Patients were aged 63.5+/-10.3 years. 82% were female. Unfavourable characteristics included age >65 (52%). NYHA class III or IV (87%), greater than or equal to 1 sigificant co-morbidity (63%), atrial fibrillation (82%), previous surgical commissurotomy (25%) and echocardiographic score >8 (59%, mean 8.9 +/- 2.1). Mitral Valve area increased from 0.98 +/- 0.23 to 1.54 +/- 0.31 cm(2). There were three major complications. Post-procedure, symptoms improved in 88% of patients. Haemodynamic success (mitral valve area increase >50% final mitral valve area >1.5 cm(2), mitral regurgitation less than or equal to grade 2) was achieved in 61% of cases. Mean follow-up was 4.3 +/- 1.4 years. Survival was 97% 88% and 82% at I, 3 and 6 years. Event-free survival (freedom from death, mitral valve replacement or repeat valvuloplasty) was 96%, 52% and 56% at 1, 3 and 6 years. Freedom from restenosis (loss of >50% gain in mitral valve area, mitral valve area <1.5 cm(2)) was 98%, 92% and 75% at 1, 3 and 6 years. Pre-procedural predictors of event-free survival were male sex, absence of comorbidities, lower echocardiographic score and smaller left atrial diameter. Conclusions In a Western population with predominantly unfavourable characteristics for mitral valvuloplasty, long-term outcome post-procedure is reasonable. A moderate increase in mitral valve area can be achieved at low procedural risk, and the subsequent rate of restenosis is low. Nonetheless, 6 years after the procedure, half of the patients will have required further intervention or died. For fitter patients willing to accept significant operative risk, mitral valve replacement remains a valuable alternative. (C) 2000 The European Society of Cardiology.