The distribution of binding sites for two lectins with different specificities was studied in adult mice by staining paraffin sections with lectins labeled either with fluorescein isothiocyanate or horseradish peroxidase. Binding sites for Dolichos biflorus agglutinin, a lectin specific to terminal alpha-N-acetylgalactosamine residue, were detected only in several restricted regions, such as collecting tubules and Bowman's capsules of the kidney, bile ducts, pancreatic ducts, sperms, oocytes, some secreting cells, and the secreted mucin itself. Binding sites for peanut agglutinin (PNA), a lectin specific to terminal beta-galactosyl residue, were distributed more widely. However, differentiation-dependent alterations in the expression of PNA binding sites have been observed in two types of cell lineage. During the course of spermatogenesis, the binding sites were expressed at the stage of spermatocytes. In the epithelium of esophagus, the binding sites were present in cells of the superficial layer.