This study was designed to investigate histological changes in the tibia of adult mongrel dogs receiving PMMA bone cement in one tibial shaft and an inert filler, Bone wax, in the other. Sixteen dogs were used, 2 dogs were investigated at one week, 6 dogs at four weeks and 8 dogs at twelve weeks. It was shown in this study, that intramedullary implantation of PMMA bone cement leads to considerable impairment of bone remodelling. At each period of observation the index periosteal apposition/cortex thickness was lower on the cemented side; at 4 weeks an index of 0.42 (0.17-0.64) compared to 0.72 (0.42-0.91), and a 60-70 microns concentric fibrillar fibrous membrane was seen between cement and bone. On the Bone wax side few or no areas of fibrous tissue were detected at both 4 and 12 weeks; and when such tissue was present, islands of bone developing directly onto the wax was seen. The bone remodelling was impaired on the cemented side and limited to the outer half after 4 weeks.