Objective: To evaluate of the role of transesophageal echocardiography (TEE)in percutaneous closure of atrial septal defects (ASD) with the Amplatzer septal occluder. Methods:Sixty-two patients (10 to 55 years of age) were selected for percutaneous closure of ASD by transesophageal echocardiography, which was also used to monitor the procedure, to select the appropriate sizeof the Amplatzer device, to verify its position, and to access the immediate results of the procedure.During the follow-up, transthoracic echocardiography ( TTE) or TEE was used to evaluate the presence and magnitude of residual shunt (RS), device position, and right cardiac chamber diameters. Results: The mean ASD diameter by TTE ( [ 19.1 ± 5.8] mm ) was significantly smaller ( P ＜0.001 ) than the stretched diameter of the ASD (25.1±6.4) mm. There are no significant differences between the TEE-measured value (23.5±6.2) mm and the stretched diameter of the ASD ( P＞ 0.05). Due to proper patient selection all procedures were successful. There was immediate and complete closure in 61/62 patients, only one patients had trivial residual shunt. Follow-up was performed using TTE or TEE right after operation, 1 d, 1 month, 3 months, 6 months and yearly thereafter. All patients remain asymptomatic without any clinical or technical problems. Conclusion: With the aid of TEE, percutaneous closure of ASD can be performed successfully, safely, and effectively.