Background: Postoperative left ventricular (LV) performance with strict application of the current guideline for surgical timing needs to be elucidated. Methods: A total of 262 patients (age 50.1짹14.0 years; 61.1% male) who underwent uneventful mitral valve surgery due to severe degenerative mitral regurgitation (MR) between Jan 2000 and Dec 2005 were enrolled. Echocardiographic (3.9짹2.3 years) and clinical follow-up (4.7짹2.4 years) data were analyzed. Postoperative LV dysfunction was defined as follow-up LV ejection fraction (EF) <40%. Results: Repair was done in 229 patients (87.4%), whereas replacement in 33 (12.6%). There was no difference in age, gender, preoperative LV size and LVEF between groups. Postoperative LV dysfunction developed similarly in both group (2.2% vs. 6.1%, p=0.216). During clinical follow-up, mortality and hospital readmission due to heart failure developed in 5 and 20 patients, respectively. Although replacement group did not show significantly higher rates of death (hazard ratio [HR] = 5.93, 95% CI, 0.94 to 37.43, p=0.059) or hospital readmission (HR = 2.38, 95% CI, 0.69 to 8.18, p=0.169), the composite clinical events of death and hospital admission developed more frequently in the replacement group (HR = 3.29, 95% CI, 1.14 to 9.49, p=0.028). The 8-year event-free survival rate was significantly higher in repair group (92.2짹2.3% vs. 67.1짹12.6%, p=0.007). Conclusions: Despite the same timing of surgery based on the current established guideline, valve replacement showed worse clinical outcomes than repair in patients with degenerative MR.