In this article we wish to describe certain effects of radiation therapy on gastric secretion in man. The studies were made on patients with peptic ulcer and with the therapy of ulcer in mind. This report, however, deals primarily with the effect on gastric secretion, because other methods of ulcer treatment were used in conjunction with x-rays and because a reliable appraisal of the therapeutic procedure is as yet premature. Bruegel1in 1917 reported the production with radiation therapy of a temporary achlorhydria as measured by means of the usual test meals in vogue at that time. Bensaude2in 1925 described a decrease in acidity in six of eleven patients. Viviani3studied the effect of radiation on histamine secretion in 1931, reporting a definite depression, variable both in extent and in duration. Emery4in 1932 noted a temporary achlorhydria in four cases. The amount of therapy