AbstractThe gradual increase with time of the insulin‐stimulated acid output, after a well‐performed parietal cell vagotomy (PCV), has been thought to be produced by regeneration of the vagus nerves. A genuine regeneration of the gastric branches of the vagus connected to the intramural plexus has yet to be confirmed. Experiments have been carried out in dogs to determine if this type of regeneration takes place after PCV.The animals were divided into 3 groups (A, B, and C) of 4 mongrel dogs each. In all dogs, a PCV was performed and the Grassi test was used intraoperatively to check the completeness of vagotomy. During the experiments, an insulin stimulation test and a macroscopic and microscopic study of the esophagus and stomach were obtained at several points in time (in group A, at operation and after 2 weeks; in group B, after 6 months; and in group C., after 2 1/2 years).We found, 2 weeks after PCV, a complete degeneration pattern of the vagal branches in the gastric serosa. After 6 months, and more completely after 2 1/2 years, many nerve fibers are seen, macroscopically, crossing from the vagus nerves and the branches of Latarjet to the esophagus and the lesser curvature through the old ligatures. This regeneration can be confirmed microscopically. These pathological changes in the nervous system of the stomach were found to correlate with recovery of gastric secretion. It is suggested that the recovery of acid secretion after a well‐performed PCV is accounted for by vagus nerves regeneration.