The effect of the chemical treatment of zirconia/alumina composites followed by a biomimetic treatment has been studied. The composites are prepared from a powder mixture of Mg- PSZ and Al2O3. The powders are ball-milled in acetone and uniaxially pressed after drying. The specimens are sintered at 1550 °C in air. After sintering, chemical treatment is performed by immersing the samples in a 5M aqueous solution of phosphoric acid at 95 °C for 4 days. The biomimetic method consists of immersing the chemically-treated samples in simulated body fluid at 36.5 °C. In some cases a wollastonite bed is used as a supplier of calcium ions, resulting in the formation of a bonelike apatite layer. The presence of this bioactive system during the biomimetic process has a positive significant effect on the bioactivation of the composites for either short or long times of immersion of the composites in simulated body fluids. The chemical treatment increases also the rate of apatite formation at short immersion periods.