A lectin histochemical study was performed to investigate the glycoconjugate saccharidic moieties of the lining and glandular epithelium of the chick embryo proventriculus from day 7 to hatching. The sugar residues D-galactose-(beta 1-->3)-N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, alpha/beta-N-acetyl-D-galactosamine and alpha-D-mannose were present at the lining epithelium of the proventriculus from the 7th day onwards; alpha-D-fucosyl residues were never detected. The same sugar residues were detected in the cells of the deep glands from the 7th day; alpha-L-fucose appeared later. The sugar residues appeared in the cells of the superficial glands at different times during the development of the proventriculus. In comparison to that of the deep glands, the secretion of the superficial glands was characterized, by the absence of N-acetylgalactosamine and alpha-D-mannose. From day 20 onwards, the composition of the mucus released by the two types of glands was identical from a qualitative point of view. The histological and histochemical results showed that the superficial glands are well defined morphological structures and not "an artefact of contraction", as claimed by other authors.