Bioactive Mg-PSZ composites were developed by using wollastonite ceramics either as a constituent of the composite formulation or as a bioactive bed during the biomimetic treatment in simulated body fluids. The zirconia composites were prepared by uniaxial pressing of powder mixtures and sintered at 1550oC in air. Wollastonite containing zirconia/alumina composites were also sintered at 1350oC. The composites were immersed in SBF for 7 days on a bed of wollastonite powder and then re-immersed in 1.5SBF for 7 days. Tests were also performed with no wollastonite bed. A highly bioactive surface was observed on the Mg-PSZ/CaSiO3 and Mg-PSZ/Al2O3 composites. A homogeneous apatite layer was detected on the Mg-PSZ/CaSiO3 composites immersed for only 7 days in SBF. No apatite was formed on the Mg-PSZ/Al2O3/CaSiO3 composite. During the sintering mechanism at either 1550 or 1350oC small amounts of aluminosilicate phases are formed. These phases inhibited the apatite formation.