All patients suspected of MR undergo transthoracic echocardiography. Entry evaluation includes demographic data, clinical presentation, physical findings and echocardiographic data. Eligibility is determined after a patient undergoes a thorough evaluation of clinical and echocardiographic data. After the eligible patient has signed informed consent, entry into the registry will take place. The treatment groups will not be randomly assigned and the choice of early surgery or conventional treatment for each patient is at the discretion of the attending physician, who explains the potential benefits of early surgery and procedural risks in detail and considers the preferences of individual patients most importantly. Patients in the early surgery group should undergo mitral valve surgery within 6 months of enrollment. Patients in the conventional treatment group will be treated according to the 2006 ACC/AHA guidelines and they will be educated to report immediately to a study coordinator or an investigator if they experience any symptoms, and referred for surgery if exertional dyspnea, LV ejection fraction <0.60, LV end-systolic dimension >40 mm, Doppler estimated pulmonary artery pressure > 50 mmHg, or atrial fibrillation develops. All patients will be followed at 3 months, 6 months, and 1 year; and at 6-month intervals thereafter until close-out of the study, and educated to call a study coordinator or an investigator if they experience any adverse events.