Carbon fiber rods were developed to provide radiolucent sidebars for external fixation. In the present study, a single-plane, half-pin, double-bar external fixator construct with either stainless-steel tubes or carbon fiber rods was applied on the anteromedial surface of an osteotomized synthetic human tibia and evaluated for fixation rigidity. Testing was performed with the bone fragments in cortical contact and with a 5-mm midshaft gap between the fragments. The sidebars then were loaded to failure in bending. The results of this study show (a) that the carbon fiber rods were 15% stiffer than the stainless-steel tubes (p = 0.009) and (b) that the external fixator with carbon fiber rods achieved approximately 85% of the fixation stiffness of the external fixator with stainless-steel tubes. The loss of stiffness of the external fixator with carbon fiber rods is most likely due to the clamps being less effective in connecting the carbon fiber rods rigidly to the Schanz screws.