The effect of shock wave therapy on acute fractures of the tibia was studied in eight adult dogs. A fracture with a 3-mm gap was created in both tibias and the fractures were fixed internally with a small metallic plate and screws. Each of the right limbs received 2000 impulses of shock waves at 14 kV whereas the left limbs were used as controls. The evaluations included the callus formations based on serial radiographic examinations at 1, 4, 8, and 12 weeks and histologic examinations at 12 weeks for tissue distribution including bone tissues. Based on radiographic findings, there was no statistically significant difference in the amount of callus formation between the treated and the control groups at 8 weeks or less. However, the radiographic findings at 12 weeks statistically showed more callus formations in the treated group. In histologic examinations, there was significantly more cortical bone formation in the treated group at 12 weeks and the bone tissues were thicker, denser, and heavier. Shock wave therapy enhanced callus formation and induced cortical bone formation in acute fractures in dogs at 12 weeks. The effect of shock wave therapy seemed to be time-dependent at 3 months.