Alumina–zirconia composites with submicrometric grain size were surface modified with the purpose to induce bioactivity using several chemical treatments. Among them, a quick attack by phosphoric acid induced on Zirconia Toughned Alumina (80–20 wt%) the formation of apatite-like calcium phosphate phases after immersion in simulated body fluid, indicating bioactivity induction. Such a treatment does not reduce the strength, hardness and ageing properties of this ceramic material, making it a suitable method for biomedical applications. Surface properties, topography and microstructure of oxide ceramics are also discussed.