Using a computerized, semi-automatic morphometrical system, the morphological effects on diaphyseal rat femur following intramedullary implantation of methyl methacrylate were studied. Furthermore a comparison with the effects of periosteal elevation and removal of the bone marrow by suction was made. The changes in bone morphology were studied with the aid of microangiography, microradiography, fluorescence microscopy and histology. The results showed that there were evident differences between the postoperative course of the three procedures regarding vascular changes in the femoral cortex, bone remodelling and extent and duration of cortical necrosis. Implantation of methyl methacrylate caused greater vascular disturbance than elevation of the periosteum and removal of the bone marrow.