Suspected partial prosthetic cardiac valve detachment can be confirmed, unequivocally in some cases, by conventional chest roentgenograms, fluoroscopy and/or cineroentgenography. This study is based upon roentgenologic examination of 54 patients with Starr-Edward’s valves and leads to a range of normal motion for both mitral and aortic prostheses. Maximal differential angulations of the prosthetic ring over 9° are abnormal. Plain roentgenograms of the chest may suggest detachment by abnormal orientation of the prosthesis; such a change must be gross to be recognized with confidence.