Sarcomas can develop in association with foreign material (eg, from Dacron vascular prostheses). We report on a left atrial rhabdomyosarcoma that developed within 1 year of mitral valve replacement by a Silzone-coated St. Jude Medical mechanical heart valve. Tumor resection and redo valve replacement were done. Six months later the patient was alive, but an echocardiogram showed tumor recurrence. Although this is a single case, an association between heart valve prostheses and malignant tumors should be considered.