The authors report the radiographic results of 65 An. C.A. prosthetic stems coated with hydroxyapatite and followed-up at least 24 months after implantation. A comparison with a homogeneous group of aluminum-coated An.C.A. stems showed that hydroxyapatite-coated stems are characterized by better osteointegration, with a clearly inferior incidence of radiolucent lines at the bone/prosthesis interface. Macroscopic observation and histologic examination carried out on two stems removed because of persistent pain to the thigh revealed partial resorption and fragmentation of the coating. The authors believe that this phenomenon, the object of other observations reported in the literature, may indicate the reduced stability of the coating in the long run, and as such further in-depth study is required.