To identify the risk factors of restenosis after balloon mitral valvuloplasty in patients with mitral restenosis after surgical valvotomy, we obtained 30.4 ± 13.0 months (range 6 to 53 months) follow-up data in 19 patients with restenosis after surgical valvotomy in whom balloon valvuloplasty was successfully performed since April 1988. There were 10 females and 9 males with a mean age of 42.7 ± 8.7 years (range 28 to 59 years). Eleven patients were in atrial fibrillation. Restenosis occurred in 8 patients (42%) during follow-up. The median value for restenosis by Kaplan-Meier survival analysis was 40 months. Restenosis by univariate analysis correlated with smaller valve area after the procedure and shortness of the interval from previous surgical valvotomy to restenosis. The independent predictors of restenosis identified by Cox proportional hazard analysis were mitral valve area after valvuloplasty (p = 0.0013) and echo-score (p = 0.0244). There was a significantly increased risk of restenosis inpatients with a post-valvuloplasty mitral valve area of less than 1.6 cm2 compared with those who had a greater mitral valve area. Patients with echo-scores greater than 8 were not significantly less likely to develop restenosis than those with echo-scores of less than 8.