Abstract: The present invention relates to acetabular cup assemblies for ball-and-socket joint protheses. The acetabular cup assembly is essentially characterized by the fact that it comprises a cup 20 of outside general shape that is substantially hemispherical, the cup including an open hollow housing 21, and an insert 23 in which a hemispherical cavity 24 is made suitable for receiving a spherical head to co-operate in rotation therewith, the insert being of outside shape that is substantially complementary to the housing 21 so as to be capable of being engaged therein, the cup 20 comprising a central base 30 constituting the polar cap of the cup 20, a determined number of cup portions 31-33, and means 34 for associating the cup portions 31-33 at least with the central base 30 to form the cup 20 with its housing 21. The invention is applicable to making a prosthesis, in particular a hip prosthesis or the like.