The purpose of this study was to determine whether low-power-consuming symmetrical-waveform electromagnetic stimuli could increase the stiffness of fracture sites in a rabbit fibular-osteotomy model. Both active and placebo devices were used in a blinded study protocol. Dose-response studies of pulse amplitude and pulse width were performed by continuous application (twenty-four hours a day) of repetitive (fifteen-hertz), bursted (five-millisecond-long) symmetrical, rectangular electromagnetic stimulus waveforms. The power consumed by these stimuli is approximately one-fifth that consumed by the pulsing electromagnetic field devices that are in current clinical use. Significant increase of callus bending stiffness was produced by pulse widths of five to seven microseconds and pulse amplitudes of fifty to 100 millivolts.