Results of 50MeV Li3+ ion irradiation on the mechanical behaviour of flux-grown YFeO3 crystals are reported. Vicker's microhardness, fracture toughness, brittleness index of the (I 10) face of irradiated YFeO3 crystals, in the load range 0.098-0.98 N, are calculated and compared with the values of unirradiated crystals. Applying the concept of Hays and Kendall, the load-independent values are estimated for the irradiated and unirradiated crystals. The decrease in the value of microhardness on irradiation is explained to be as a result of amorphization in the material. Classification of cracks is dealt with and it is reported that the transition from Palmqvist to median type of cracks occurs at higher loads. The average values of fracture toughness, brittleness index and yield strength are also determined for the irradiated crystals. (c) 2005 Elsevier B.V. All rights reserved.