The author has determined the pepsin-like substance, so-called uropepsin, in the urine by the method of Bucher and Mirsky. Results obtained were as follow. The uropepsin decreased considerably in the stomach cancer, and increased in the gastric and the duodenal ulcers. In the chronic gastritis the uropepsin was moderate in amount, which was less than that in the healthy stomach. No relation has been observed between the gastric acidity and the uropepsin level; The uropepsin level was not correspond to the peptic secretory activity of the stomach. There were some cases showing high uropepsin level after gastrectomy on the duodenal ulcer. The author has concluded that the uropepsin production had been promoted by the operation which had given an influence to the adrenal gland as a kind of stress.