We present herein the cases of two patients who were diagnosed as having thrombosed tricuspid valves by electrocardiography after undergoing valve replacement with Starr-Edwards caged ball valves for Ebstein's anomaly 19 and 27 years earlier. In both patients, the valves were found to be attached to the right ventricular septum and covered with massive thrombus, the balls being completely jammed in a half-open position in the cages. Re-replacement of the valves was successfully performed with Hancock II porcine heterograft prostheses and both patients are now classified as being in Functional Class I or II.