This part of ISO 6474 specifies the characteristics of, and corresponding test methods for, a biocompatible and biostable ceramic-bone-substitute material based on a zirconia-reinforced, high-purity alumina matrix composite for use as a component in orthopaedic joint prostheses. This part of ISO 6474 is intended for composite materials which are based on an alumina matrix, i.e. alumina as the dominating phase in the composite with a mass fraction of > 60 %, similar to the material described in ISO 6474-1, but extended by means of a certain amount of zirconia and other defined ingredients. NOTE The required properties in this part of ISO 6474 differ from those in ISO 6474-1 with respect to strength and fracture toughness. Furthermore, there are requirements specifically applicable for zirconia-containing materials (see ISO 13356). In the material composition as defined in this part of ISO 6474, additional additives are listed. Typical additives for alumina or zirconia ceramics are Mg, Y, Ce and others. Such additives can be useful in order to improve the mechanical properties and/or the chemical stability of the alumina-zirconia composite material. This part of ISO 6474 does not cover the biocompatibility (see ISO 10993-1) of these inorganic additives in the human body. It is the responsibility of the manufacturer to evaluate the biocompatibility of the specific ceramic composite material which is produced within the framework of this part of ISO 6474.