The goals of internal fixation are an accurate reduction and stable fixation in the presence of adequate bony vascularity. This can be achieved by a variety of means including plate fixation. A certain amount of periosteal stripping is necessary for proper open reduction of a fracture and for proper plate application. With displaced diaphyseal fractures, cortical bone perfusion (CBP) is already compromised. Further damage, in terms of periosteal stripping for plate fixation, may not be acceptable. Little information is available as to what extent the periosteum contributes to cortical bone perfusion. The purpose of this study was to determine the acute effects of periosteal stripping on cortical bone perfusion in a sheep tibia model. Twenty-three sheep were operated on and had the medial aspect of their right tibia exposed. Cortical bone perfusion measurements were obtained using laser Doppler flowmetry prior to periosteal stripping and after periosteal stripping. The results of this study show that the cortical bone perfusion significantly decreased by 20% after periosteal stripping over the entire length of the tibia. We therefore conclude that the periosteum contributes to diaphyseal bone perfusion and that it is important to preserve this source with fractures where blood supply is already significantly compromised.