In order to investigate the morphological and functional changes produced in the colonic mucosa after prolonged exposure to gastric juices, 24 colonic patches were implanted on the gastric body and the gastric antrum. The specimens were removed, two, four or six months after surgery, and several morpho-functional changes were observed. These included a gastric-like transformation of the superficial epithelial cells, the presence, exclusively in the colonic patches implanted in the gastric body, of cells with large osmiophilic cytoplasmic granules and a progressive increase in sialomucin secretion with an almost complete disappearance of sulfomucins.