The present studies were carried out to asses the release of secretin after a gastrectomy with special reference to the difference in the re-establishment of continuity, i. e., whether it is Billroth Ⅰ procedure or Billroth Ⅱ.A. Clinical Studies 1. The fasting serum secretin level was 140±50pg/ml in healthy individuals (control), 144±59pg/ml in patients with stomach cancer, and 172±52pg/ml in patients with stomach ulcers. No statistically signficant differences were found between control and the patient groups. It was noteworthy that the serum secretin levels were the highest (194.4±44pg/ml) in mild cases of duodenal ulcer which were treated medically and the lowest (130±37.6pg/ml) in less mild cases…