THE METAL tantalum has been shown to be inert and well tolerated by body tissues.1 It has been widely used for the repair of defects following wounds of the skull sustained in war in the form of tantalum plate.2 The material is also available and used as tantalum foil and tantalum suture material.3 In the case to be presented a large sheet of tantalum 0.0125 inch (0.032 cm.) thick was used as a prosthesis after removal of the body of the sternum and a large part of the anterior thoracic wall for osteochondrosarcoma originating in the sternum. It was hoped that the tantalum plate might serve as a permanent prosthesis. However, the motion of the thoracic wall produced so much bleeding from the tissues surrounding the plate that formation of hematoma necessitated removal of the plate. The plate did, however, serve as a valuable temporary prosthesis to