Consequently, incorporation of Mg2+ ions into HAp lattice is of great interest for developing bone graft materials with superior bioactivity and unique biological behaviour in orthopaedic and dental applications. According to literature, replacement of calcium by magnesium in HAp structure is limited [1,2]. Usually, the incorporation of Mg in synthetic HAp is about 0,4 wt% [2]. However, maximal amount of Mg2+ ions substituting for Ca2+ ions varies widely in range of 0.3-29.0 wt%. Contradictions in previous studies about Mg-substituted HAp materials motivated the authors to synthesize and investigate magnesium-substituted HAp materials. The objective is to prepare pure and Mg-substituted hydroxyapatite (HAp) bioceramics with different Mg concentrations and investigate the effect of Mg2+ ions incorporated into HAp lattice structure on the properties of synthesized and sintered HAp materials. In this work HAp and Mg-substituted hydroxyapatites (Mg-HAp) were synthesized by modified wet chemical precipitation of homogenous suspension of Mg(OH)2 /(Ca(OH)2 and H3PO4 solution. MgO was added in synthesis media in the wide range of 0.1-20.0 wt% in respect to CaO. The Mg-HAp bioceramics have been prepared with different Mg incorporation levels (from about 0.21 to about 4.72 wt%). Systematic investigation on as-synthesized and sintered Mg-HAp and HAp samples shows that the incorporation of Mg2+ ions promotes decomposition of HAp to Mg-substituted β-tricalcium phosphate (Mg-substituted β-TCP) and significantly modified HAp crystallites morphology and microstructure after thermal treatment. It was considered that incorporation level of Mg into HAp lattice structure will depends on the synthesis method used in Mg-HAp synthesis process. Referneces [1] I. Cacciotti, A. Bianco, M. Lombardi, L. Montanaro, Mg-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sintering behaviour, J. Eur. Ceram. Soc. 29 (2009) 2969-2978. [2] W.L. Suchanek, K. Byrappa, P.Shuk, R.E. Riman, V.F. Janas, K.S. TenHuisen, Preparation of magnesium substituted hydroxyapatite powders by the mechanochemical-hydrothermal method, Biomaterials 25 (2004) 4647-4657.