Many procedures have been proposed for the treatment of traumatic painful instabilities of the Distal Radio-Ulnar Joint (DRUJ). Moore-Darrach, Milch, Baldwin, Bowers, Kapandji-Sauvé. Except for the Milch procedure, the risk of painful instability of the ulnar stump is real, but not very frequent if the technique is correctly applied. When this complication occurs, the best way to ensure the ulnar stump stabilization is mechanical, by mean of a DRUJ Prosthesis which we were the first to imagine and build. Used in two cases, with or without remnant ulnar head, these two types of prosthesis seem to have been favourable. Obviously, it is too early to know the final value of this prosthesis, based only on two cases, but it seemed important to make it known as an additional possibility in the treatment of the DRUJ problems. These two types of prosthesis are conceived on original principles: cementless fixation but with screws and nuts giving immediate and definitive stability and allowing a fast rehabilitation. The articular pieces are composite, metal on H.D. Polythylene. The articular surface is spherical permitting all the mobilities of this complex joint. The two articular surfaces are supported by two pieces: the proximal part, holding a hollow hemisphere, inserted in the ulna and the same for the two types of prosthesis, and a distal part, holding the sphere; this part is different according to the type of the prosthesis. We are well aware that in time and with clinical experience, some of its secondary characteristics will evolve, mainly its fixation system. At the present time this prosthesis is indicated in two "second look" situations: painful ulnar stump instability after a Kapandji-Sauvé procedure, and after a Moore-Darrach procedure. Perhaps it will be used in unstable stumps after a Bowers procedure? It is possible that this prosthesis will be used primarlly in the future when its reliability has been definitively established. We are working towards this objective.