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Evaluation of toughening behaviour of the tetragonal phase of zirconia can be made with Raman spectroscopy, which is a useful method to define a correlation model between toughness and transformability. Raman analysis is based on the quantitative mapping of zirconia phases (tetragonal, monoclinic) around Vickers indentations and along cracks which yield indications about transformability of the tetragonal phase. On the basis of these considerations, zirconia-alumina composite were characterised following this procedure: first of all, indentation data were analysed with the aim of defining crack type (median crack or Palmqvist) in order to choose the right equation to calculate KIc. After this, Raman analysis were performed around Vickers indentation to determine the Transformation Zone Size (TZS) and volumetric fraction of monoclinic phase (Vf). These parameters were correlated to toughness and the results were compared to data reported in literature.