Enhancement of the fracture toughness of Al2O3 was achieved by the additions of 10-40 vol% Cr3C2 particulates through a hot-pressing process. The dependence of Cr3C2 particle size (0.5, 1.5 and 7.5 mu m) on the toughening effect was investigated. The maximum fracture toughness of composites could be improved to 5.9, 7.6 and 8.0 MPa m(1/2) for fine, medium and coarse Cr3C2 particle reinforced composites, respectively. Both the quantitative analysis of toughening contributions and experimental observations are extensively discussed in terms of Cr3C2 particle size, microcracks, as well as thermal residual stress between Al2O3 and Cr3C2.