This document specifies the characteristics of, and corresponding test methods for bio-stable ceramic-bone-substitute material based on a zirconia-reinforced, high-purity alumina matrix composite for use as bone spacers, bone replacements and components in orthopaedic joint prostheses. This document 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 document 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 document, 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 document does not cover biocompatibility (see ISO 10993‑1). 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 document.