The gastric secretion after different types of vagotomy was studied in experiments on dogs and in clinic. The ordinary selective proximal vagotomy (SPV) and the truncal vagotomy were successively performed in one and the same animal and the secretion of the Pavlov and Heidenhein stomachs was investigated. The cerebral phase of secretion proved to be inhibited similarly after all the types of vagotomy. As to the ventricular phase, it was most of all decreased following SPV without a draining operation. The clinical part of the work covers 148 patients with duodenal ulcers subjected to SPV without a draining operation (51 patients) and in combination with pyloroplasty (97 patients). The investigation of gastric secretion in these patients has shown the greatest decrease of it to occur after SPV without a draining operation. The same findings show that after SPV without a draining operation the damping syndrome and diarrhea are observed rarer than after all types of vagotomy combined with pyloroplasty.