A 52-year-old woman who was suffering from easy fatigability and arrhythmia underwent MVR using a Duromedics prosthetic valve and TAP with DeVaga's technique in November 1985. She was doing well postoperatively with Warfarin, until July 1988 when cinefluoroscopy showed one of the leaflets to be immobilized in the closed position and the other with full range of motion. The patient underwent re-MVR using a St. Jude Medical prosthetic valve. She is doing well 14 months after surgery. The diagnosis and management of thrombosed bi-leaflet mechanical valve prosthesis was also discussed.