The aim of this randomised, controlled in vivo study in an ovine model was to investigate the effect of cyclic pneumatic pressure on fracture healing. We performed a transverse osteotomy of the right radius in 37 sheep. They were randomised to a control group or a treatment group where they received cyclic loading of the osteotomy by the application of a pressure cuff around the muscles of the proximal forelimb. Sheep from both groups were killed at four or six weeks. Radiography, ultrasonography, biomechanical testing and histomorphometry were used to assess the differences between the groups. The area of periosteal callus, peak torsional strength, fracture stiffness, energy absorbed over the first 10 degrees of torsion and histomorphometric analysis all showed that the osteotomies treated with the cyclic pneumatic pressure at four weeks were not significantly different from the control osteotomies at six weeks.