Though gastric tubes are most frequently used for reconstruction of esophagus, high rate of suture insufficiency at the site of anastomosis including minor leakage still remains as a nuisance problem. As causes for suture insufficiency at the site of anastomosis, not only systemic factors such as hypoproteinemia, pulmonary function disorder, etc. but also local factors such as insufficient blood flow in gastric tube, mechanical tension on the suture site, etc. have been pointed out. The author studied hemodynamics of the gastric tube in mongrel dogs under various conditions in detail with hydrogen gas clearance method and obtained the following results. 1. When gastric tube of greater curvature with diameter of about 3 cm (hereinafter referred to as gastric tube) is made from the whole gastric tube of one dog, tissue blood flow of the oral end of the gastric tube increased by 76%. 2. When tension of 500 g was loaded to the gastric tube in the direction toward head, tissue blood flow of the oral end of the gastric tube decreased by 12%. 3. When the gastric tube was incised circumferentially through seromuscular layer, tissue blood flow of the oral end of the gastric tube made no remarkable change. 4. In the gastric tube, measurement of tissue blood flow was possible from the terminal pulsating branch of the right gastroepiploic artery for 6 cm toward the oral site. Tissue blood flow decreased as the site of measurement became closer to the oral edge of the gastric tube in proportion to the distance. In the cases whose sutures were performed at 3 cm and 4.5 cm oral from the terminal pulsating branch of the right gastroepiploic artery, any leakage was not seen. However in 2 cases of 5 whose sutures were performed at 6 cm, leakages were observed. 5. When sympathetic nerve around the common hepatic artery was removed, tissue blood flow of the gastric tube increased as much as 53%. 6. In cases whose sympathetic nerve were untouched, tissue blood flow of the oral end of the gastric tube was measured everyday for one week after the operation. For three days after operation, the blood flow remained low but from the 4th postoperative day it gradually increased and on the 7th postoperative day it was about 45% of that of preoperative stomach and 124% of that at the time of the gastric tube preparation. 7. In cases with sympathetic nerve resection, the tissue blood flow of the oral end of the gastric tube was observed for one week after operation.(ABSTRACT TRUNCATED AT 400 WORDS)