AbstractSeveral glycoconjugates are thought to bind spermatozoa as they pass through reproductive ducts. Paraffin sections of testis, ductuli efferentes, epididymis, and vas deferens of male mice were stained with ten different lectin‐horseradish peroxidase conjugates to localize possible sites of synthesis and secretion of such glycoconjugates, based on the carbohydrate moieties in their constituent oligosaccharide side chains. Principal (columnar) cells lining the efferent ducts, germinal epithelium, and developing and maturing spermatozoa were examined with light microscopy. Staining of the Golgi and apical zones of cells was interpreted as evidence for synthesis and secretion of glycoconjugates. Principal cells synthesized and secreted glycoconjugates with sugar moieties as follows: sialic acid, all regions of the efferent ducts examined; the terminal disaccharide D‐galactose‐ (β1 → 3) ‐N‐acetyl‐D‐galactosamine, all regions of ducts except epididymis I; terminal α‐D‐galactosamine, some cells in epididymis III‐V; N‐acetyl‐D‐galactosamine, ductuli efferentes, epididymis I, II, and some cells in epididymis III‐V; α‐L‐fucose, ductuli efferentes, vas deferens, and all regions of the epididymis except IV; N‐glycosidic side chains, ductuli efferentes, vas deferens, and epididymis I, IV, and V. All of these sugar residues as well as N‐acetyl‐D‐glucosamine were associated with the acrosomes and tails of spermatozoa throughout the ducts except for α‐N‐acetyl‐D‐galactosamine in epididymis I, and all occurred during one or more stages of spermiogenesis. The synthesis and secretion of glycoconjugates that bind to spermatozoa appear to involve more regions of the primary