The transition of mild to severe wear of ceramics depends on the operating conditions (normal load, velocity and temperature) and material properties (like grain size, mechanical and thermal material properties). Adachi et al. [Wear 203¿204 (1997) 291] introduced the transition of mild to severe wear of ceramics by defining a mechanical severity parameter based on the work of Hamilton [Proc. Inst. Mech. Eng. 197C (1983)] and a thermal severity parameter based on the work of Ashby et al. [Tribol. Trans. (34) (1991) 577]. Metselaar et al. [Wear 249 (2001) 962] improved the thermal severity parameter using the temperature model introduced by Bos [Frictional heating of tribological contacts, Ph.D. Thesis, University of Twente, 1995]. Better prediction of wear transition in the region where the transition is dominated by thermally induced wear was achieved. The combination of the mechanical severity parameter and the thermal severity parameter for Peclet number (Pe) higher than 2 is presented in this paper. This model is verified experimentally and gives an improved prediction of the mild to severe wear transition of ceramics.