The purpose of this study was to assess the effects of high doses of ionising radiation on the histology and healing of bone in an experimental model of 12 inbred rats. Ten of the rats had external irradiation of a single dose of 30 or 45 Gy on the hind limbs, which is equivalent to 2 or 3 times the routine doses used for treatment in humans. Three weeks later, two bony defects were created on their left sides, and the animals were killed 12 or 18 weeks after irradiation. Decalcified bony specimens were studied with light microscopy for qualitative analysis. Thirty Gy irradiation induced medullar oedema or fibro-oedema and normal or fibrous healing of the defects. Forty-five Gy induced medullar oedema or fibro-oedema and depletion in bone marrow. In addition, pathological healing of the defects was obvious and characterised by oedema, fibrosis, and necrosis. In this study high doses of ionising radiation modified the histology of bone, particularly into fibro-oedema, and delayed healing. This new animal model could be used to evaluate the capacities of tissue-engineered materials to repair bony defects after irradiation and osteoradionecrosis.