We showed antisecretory effects of peptides of PGP, semax and a new pancreatic hormone, amylin, on the model of continuous stomach perfusion with the registration of pH, PCO2 as well as the determination of the amount of pepsinogen in the stomach perfusate. The intraperitoneal introduction of these peptides in the doses that proved to have an apparent anti-ulcer effect caused a decrease of both basal production of hydrochloric acid in the stomach and production caused by the irritation of the vagus nerve. Semax and amylin also decreased basal and stimulated secretion of pepsinogen. Amylin and PGP did not have any effect on basal bicarbonate secretion of the stomach, and semax caused its short-time increase 35 minutes after the introduction. We made a conclusion that the decrease of aggressive factors in gastric juices can be a mechanism of the anti-ulcer action of all three peptides under study.