The development of mitral stenosis (MS) is not uncommon after mitral valve (MV) repair for degenerative mitral regurgitation (MR), but the significance of MS in this setting has not been defined.We prospectively studied 110 such patients who underwent supine bicycle exercise testing to assess intracardiac hemodynamics at rest and at peak exercise. B-type natriuretic peptide (BNP) levels were measured at rest and after the exercise test. The patients also performed the 6-minute walk test and completed the 36-Item Short Form Survey (SF-36). Follow-up was performed by a review of the medical record and telephone interview.Of 110 patients, 22 had MS defined by a mitral valve area (MVA) ≤ 1.5 cm2. The resting and peak exercise mitral gradients and pulmonary artery systolic pressure were significantly higher in patients with MS compared with patients with an MVA > 1.5 cm2. BNP levels at rest and after exercise were also higher in the patients with MS, who also had lower exercise capacity and worse perception of well-being in 3 domains (physical function, vitality, and social function) on the SF-36. MVA had higher specificity and positive predictive value in predicting outcome events compared with a mean gradient of 3 or 5 mm Hg.In patients who had MV repair for degenerative MR, an MVA ≤ 1.5 cm2 occurs in about one-fifth of patients and is associated with adverse intracardiac hemodynamics, lower exercise capacity, and adverse outcomes.