The development of the esophagus in the chick embryo is characterized by remarkable morphological changes especially at the level of the epithelium. Using horseradish peroxidase-conjugated lectins (DBA, PNA, SBA, WGA, ConA LTA, UEAI) we have studied, at the level of the esophagus of chick embryos from the 8th to the 21st day of incubation and of 1- and 2-day-old chicken, the evolution of the saccharidic moieties of glycoconjugates, which precedes and/or is concomitant with the epithelial morphological transformations. We have found differences in content and cellular distribution of oligosaccharides during the histogenetic processes which characterize the lining and glandular epithelium. Before the appearance of cilia and mucus secretion at the bathyprismatic epithelial cells, the sugar residues D-galactose-(β1 → 3)-N-acetyl-D-galactosamine, β-N-acetyl-D-galactosamine and α-L-fucose were detected only at the luminal cell surface. These oligosaccharides were probably involved in giving rise to the polarization of the esophageal epithelial cells. The esophageal gland mucus was first characterized by the presence of α-L-fucose and afterwards also by the presence of D-galactose-(β1 → 3)-N-acetyl-D galactosamine D-glucosamine and sialic acid.