Abstract： Objective To improve therapeutic outcomes for severe leftsided atrioventricular valve regurgitation (LAVVR) after repair of atrioventricular septal defect (AVSD) through discussing pathological changes of the valve and surgical management for these patients, and summarizing the medical experiences of perioperative managements. Methods We retrospectively analyzed the clinical data of 29 patients including 16 males and 13 females with LAVVR after repair of AVSD treated in Xinhua Hospital, Medical College of Shanghai Jiaotong University between January 1995 and December 2009. The age of these patients ranged from 4 to 62 years, averaging at 26.5. According the classification of New York Heart Association (NYHA), there were 10 patients of class Ⅱ, 17 of class Ⅲ and 2 of class Ⅳ before reoperation. Partial repair of AVSD had been carried out for 18 patients, and complete repair had been performed on 11 patients. At reoperation, valve rerepair was performed on 17 patients and mechanical valve replacement (MVR) was necessary in 12 patients. Results In the early period after operation, one patient died of multiple organ failure, one patient had a permanent pacemaker inserted because of complete atrioventricular block, and 1 patient aged 4 years got recovery after 56 hours of circulatory support for severe cardiac failure after reoperation. A mean follow-up of 8.2 years (6 months to 14 years) was done for 25 patients with 3 missing. During the follow-up for 14 patients undergone heart valve repair, there was no obvious acceleration of the forward blood flow of the leftside atrioventricular valve. Ten patients had mild or less LAVVR, 1 had moderate LAVVR and 3 underwent successful left atrioventricular valve replacement at 10 days, 3 years or 6 years after reoperation because of severe LAVVR. Clinical status, as assessed by the NYHA classification, improved after surgery for LAVVR in 25 patients who were followed up with 17 in NYHA class Ⅰ, 6 in class Ⅱ, and 2 in class Ⅲ. Podoid decreased significantly and cardiothoracic ratio was 0.53-0.67 (0.60±0.11) in chest Xray picture. There was no late death. Conclusion With timely surgical treatment, and appropriate surgical method, LAVVR after complete or partial AVSD repair can be managed with excellent shortterm and longterm outcomes.