This study was performed to determine the effects of anastomosis on the internal diameter and wall thickness of jugular vein. Tro shepherd dogs were used for this experiment. In dog 1, xylazine(2 mg/kg) and ketamine(5.5 mg/kg) were injected intramuscularly for induction followed by enflurane(3%) anesthesia. In dog 2, acepromazine(0.03 mg/kg) and ketamine(5 mg/kg) were injected intravenously for induction followed by enflurane(3%) anesthesia. The dogs were heparinized(1 mg/kg) for the prevention of thrombosis. After jugular vein was exposed by incision of left cervical area, two Johns Hopkins bulldog clamps were clamped. Jugular vein was cut between two clamps, and it was reanastomosed using 5-0 silk. Ultrasonography was done along the jugular vein on both sides of each dogs 21 days after anastomosis surgery. The internal diameter and circumference of the vein in the anastomosis area were markedly reduced with thickening of the vein wall, but no thrombi were observed.