Over the last decade, hydroxyapatite (HAp) has been of special interest to dentistry, the orthopedic industry and nanomedicine because of their excellent performance. It is established that nanosized and nanocrystalline HAp can mimic the dimensions of mineral component of calcified tissues. The major inorganic component of bone mineral is a biological apatite, which can be defined as a non-stoichiometric, carbonated, ionsubstituted and calcium deficient HAp (CDHAp). The non-stoichiometry of biological apatites arises from the incorporation of foreign ions, either into the crystal lattice or adsorbed onto the surface. Substituting ions present in native hard tissues such as Sr, Mg, and Zn into HAp structure can lead to advantageous effects on biomaterial physic-chemical properties which directly influence bioactivity on living system. In order to investigate the influence of Sr and Mg incorporation on the physico-chemical properties of nanocrystalline HAp we have prepared compositions of pure, Sr- and Mg-substituted HA by a low temperature aqueous precipitation.