Our clinical experiences of treatment for definite or probable thrombosed mechanical valve prostheses was presented and discussed concerning with surgical indication, several operative approaches to a target valve and detail surgical techniques. Preoperative diagnosis includes loss of metallic click sound, abnormal restricted disc movement and echocardiographic evidences of annular, occluder or housing thrombus. Valve re-replacement or thrombus removal was performed with re-do sternotomy or thoracotomy in urgent or elective cardiopulmonary bypass. Careful preparation of right atrium, superior and inferior vena cava and ascending aorta, and establishment of moderate hypothermic cardiopulmonary bypass were essential for re-replacement of the thrombosed valve. Among 15 patients, mitral re-replacement was performed in 10, aortic re-replacement in 3, tricuspid re-replacement in 2 and thrombus removal in 1. Hospital mortality rate was 6.7%, and late recurrence of thrombosed valve was observed in a patient. Pathophysiology of thrombotic process and bioactivity on the prosthetic valves are yet unsolved. Further refinement of clinical strategy would be necessary in relation to the effect of antithrombotic and antiinflammatory treatment.