Background: The development of significant tricuspid regurgitation (TR) long after mitral valve replacement (MVR) may contribute to increased morbidity and mortality. But it is not known whether significant TR following percutaneous mitral valvuloplasty (PMV) may increase the mortality and morbidity. And it also remains to be elucidated what is the predictor of significant TR long after PMV. Methods: PMV was performed in 247 patients (female: 198) between August 1988 and October 1998 with double balloon. The mean age was 40짹11 years.Mean clinical follow-up duration was 103 months (range: 24-200 months) and the mean echocardiographic follow-up duration was 104 months.The significant TR was defined as moderate or severe TR on echocardiography. We investigated the long term follow-up events (death, cerebrovascular attack,redo PMV, mitral valve replacement)of PMV by the severity of TR and the risk factors for developing significant TR long after PMV. Results:The incidence of significant TR long after PMV was 41patients (16.6%), which was 32 (13 %) in moderate and 9 (3.6%) in severe TR. The atrial fibrillation (AF) and normal sinus rhythm (NSR) were 96(38.9%) and 151(61.1%), respectively. There was a significant difference in significant TR rate between AF and NSR, 26.0% and 10.6% respectively (p=0.001). The long term follow-up event rate was higher in the group with significant TR but statistically not significant.(19.4%: 29.3%, p=0.16). However in man, the event rates long after the PMV were higher in significant TR group (8/41=19.5%) than in mild or trivial TR groups (5/8=62.5%) with statistic significance (p=0.023). The predictor of significant TR were AF (p=0.001), TR pressure gradient immediate after PMV (p=0.03) and age over 55 (p=0.008) by univariate analysis. But by multivariate analysis, AF (p=0.004, OR=2.98, CI 1.42-6.26) and TR pressure gradient immediate after PMV (p=0.003, OR=1.03, CI 1.01-1.06) were identified as statistically significant predictors of late TR. Conclusion: Significant TR may develop long after successful PMV and may increase the event rate than lower grade TR in man. Risk factors for TR long after PMV were atrial fibrillation and TR pressure gradient immediate after PMV.