Background. Mitral stenosis (MS) is a valvular heart disease that can be commonly encountered in developing countries. Although percutaneous mitral valvuloplasty (PMV) is an attractive therapeutic option for MS, whether it reverses tricuspid regurgitation (TR), a commonly associated valvular abnormality in MS and its relationship to clinical outcomes has not been investigated in the long-term. Methods. We analyzed a prospective cohort of 299 patients who underwent successful PMV from 1988 to 2010. The echocardiographic endpoint was significant TR more than moderate degree. The clinical endpoint was TV-related event, composite of TV-related procedure, admission for decompensated heart failure and cardiac death. Results. Median follow-up was 12 years (IQR 8.0~18.00 years). 56 patients (18.7%) developed significant TR during follow-up, the incidence of which increased time dependently (9.4%, 19.8% and 35.2% at 8, 12, and 18 years) and the pattern of which identical for TV-related events (38 events, 4.4%, 9.5% and 32.4% at 8, 12, and 18 years). Significant predictors of late TR were atrial fibrillation (AF) at baseline, pre-PMV TR���moderate and final MVA at follow-up (HR 1.209~8.855 for AF, p-value=0.020; HR 1.056~2.760 for pre-PMV TR��� moderate, p-value=0.029; HR 0.038~0.666 for final MVA, p-value=0.012), which was also similar for predictors of TV-related events. Final MVA of 1.50~1.55cm2 was best predictive of significant TR development and TV-related events. Patients with restenosis (final MVA<1.50cm2) were 5.0-times (HR 1.5~16.2, p-value=0.008) and 6.0-times (HR 1.3~28.0, p-value=0.022) more likely to develop late TR and TV-related events compared to those without. Conclusion. Late TR develops in a time-dependent manner after PMV. Patients with atrial fibrillation and significant TR at baseline and those developing restenosis of the MV are more likely to develop late TR. These findings underscore careful selection of candidates for PMV and also emphasize the possible close relationship between MS and TR.