IN 1961, Starr and Edwards reported their first clinical experience with a ball-valve prosthesis as a replacement for the mitral valve.1In 1963, these authors and their colleagues described their initial experience with a similar device for complete replacement of the aortic valve.2The literature on the subject suggests that hundreds of diseased aortic valves have been replaced by the Starr-Edwards ball-valve aortic prosthesis in the past 20 months. In a number of instances multiple valves have been replaced.3,4The authors have uniformly been interested in the late follow-up results, but none to date has reported migration of the ball from its metal cage. This report will describe such a complication. Report of a Case A 56-year-old male truck driver was admitted to the Lower Bucks County Hospital, Bristol, Pa, with acute failure of the left ventricle. He had the harsh systolic aortic murmur and thrill and