Total detachment and embolization of the hinged, tilting occluder of the Wada-Cutter prosthetic heart valve was the proved cause of death in 2 of 25 patients who had these devices implanted at the University of California, San Francisco, Medical Center in 1969-70. In addition, there were 8 late deaths without postmortem examination, 2 of which were sudden and 4 of which followed rapidly progressive congestive heart failure over a period of hours to days. Prosthetic malfunction appears to be a possible mechanism of death in the majority of these patients. The 2 additional late deaths were unrelated to valve malfunction. Regurgitant murmurs have been identified during follow-up examination in 17 patients. Two patients had prosthetic replacement for hemodynamically significant leaks through the valve mechanism and were found to have no perivalvular leak. Six additional patients had prophylactic replacement of the Wada-Cutter valve. Measurements on 7 available occluders that were removed showed variable degrees of material movement at the hinge. This experience has caused us to recommend elective replacement of remaining Wada-Cutter valves.