Using immunohistochemistry, seven markers associated with mucous glycoproteins were studied in rat colonic mucosa during fetal and adult life and in carcinomas. These included: blood group A antigen, terminal fucose, sulfated and sialylated groups, M3 intestinal, M3C colonic and M1 gastric antigens. It was found that colonic carcinomas expressed normal adult markers, fetal markers and an ectopic marker. The differentiation of goblet cells was not the same in distal and proximal colon. Finally, this differentiation shared numerous analogies with that of human colonic goblet cells.