OBJECTIVE: Systemic embolism related with left atrial thrombi is a well known complication of percutaneous ballon valveloplasty of the mitral valve stenosis. The presence of left atrial thtombi is believed to be a contraindication to balloon valvuloplasty. The purpose of this study was to determine whether balloon valvuloplasty is possible in mitral stenosis patients with left atrial thrombi after oral anticoagulation therapy. METHODS: We studied 13 consecutive patients(12 : female, 1 : male, mean age : 44+/-11) who had mitral stenosis and left atrial appendage thrombi by serial transesophageal echocardiography before balloon valvuloplasty of the stenotic mitral valve from May 1995 to January 1997. We started oral anticoagulation in those 13 patients with mitral stenosis and left atrial appendage thrombi to keep the INR 2-3. Regular follow up was performed by transesophageal echocardiagraphy to determine whether the left atrial appendage thrombi are resolved. Patients underwent percutaneous balloon valvuloplasty after complete resolution of left atrial appendage thrombi. RESULTS: 9 patients(69.2%) underwent balloon valvuloplasty after complete resolution of left atrial appendage thrombi with oral anticoagulation for average 6 months. Two (15.4%) patients had normal sinus rhythm. Three patients had coronary A-V fistular due to neovascularization to left atrial appendage thrombi. In four patients, oral antiocoagulation failed to resolve the left atrial appendage thrombi and they underwent balloon valvuloplasty under TEE guide with special caution to avoid systemic embolization. There were no complications such as systemic embolization in those 4 patients. CONCLUSION: Left atrial appendage thrombi in mitral stenosis could be resolved in high proportion(69.2%) by oral anticoagulation therapy. Percutaneous mitral balloon valvuloplasty could be a safe and effective treatment modality despite of the presence of left atrial appendage thrombi after adequate oral anticoagulation therapy.