This study was focused on the bone tissue response to cement in failed hip joint prostheses. The investigation was carried out by means of micro-beam X-ray diffractometric (XRD) analysis of the bone-cement interface. Nine cemented prostheses retrieved because of loosening were studied. This research has demonstrated that the newly formed bone close to the cement in loosened prostheses showed a normal apatitic structure, though bone tissue was often found poorly mineralized. In contrast, in stable prostheses well-mineralized bone was observed. In both cases, however, the bone apatite lattice at the interface was shown not to be different from pre-existing bone. The authors conclude that the mineralization process close to the cement can be thoroughly evaluated by micro-beam XRD techniques. © 1994 Chapman & Hall.