Abstract: Arrangement consisting of an acetabular cup prosthesis and of an implantation instrument for same. The acetabular cup prosthesis has at least one undercut holding recess in its edge end face. The instrument has a block which fits with centring into the opening or onto the opening edge of the acetabular cup prosthesis, and at least one holding projection positionally assigned to the holding recess and fitting into the latter, which holding projection is movable transverse to the opening direction, can be locked in a position in which it catches in the undercut of the holding recess, and can be withdrawn therefrom by means of an actuating member.