Jejunal or colonic segments are currently used as esophageal substitutes after resection of intractable peptic stenoses. The present study was carried out in order to investigate the effects of the jejunal or colonic mucosa on antral gastrin (G) cells. Colonic or jejunal patches with intact vascular supply were sutured to the pyloric antrum or the higher portion of the gastric body in 40 rats. Ten further animals were used as controls. Three to 4 months after surgery, the serum gastrin levels were weekly determined in fasted (24 h) and freely fed rats using radioimmunoassay. The pyloric antrum was then removed, and the G cell density was assessed with an immunoperoxidase method. Transposal of the colonic mucosa to the antrum increased G cell density and basal serum gastrin levels, while grafting of the jejunal mucosa did not. G cell proliferation proved to be dependent on the topographic location of the colonic patch with respect to the pyloric antrum. Serum gastrin values in freely fed rats tended to be greater in the colon-to-antrum transposition group than in the other experimental groups, but the difference was not significant. In conclusion, variations between the properties of the jejunal and colonic mucosa would include their uneven effects on antral G cells.