We performed a preliminary study to evaluate the effect of ultrasound in canine osteotomy model. Both ulna shafts were osteotomized and one side was irradiated with low-energy pulsing ultrasound, 50mW/cm2, 1 MHz, 200 microsecond bursting sine wave for 15 minutes, 6 days a week. Effect on the fracture healing was evaluated by radiologic scoring system, amount of uptake of radioactive isotope, and time to union. Results were as follows : At postoperative 2 months, means of the radiologic healing score were 4.5 in the irradiated side and 2.5 on the control side (p=0.019). Mean isotope uptake in the irradiated side was 44.4 count and 33.8 count in the control side (p=0.028). Two nonunion developed on the control side. Mean time to union of eight dogs was 2.6 months in the irradiated side and 3.1 months on the control side. Based on the cumulative union rate curve, fracture healing was stimulated and union was obtained one month faster in the irradiated side than the control side.