Fluorescein isothiocyanate-conjugated concanavalin A (F-conA) and soy bean agglutinin (F-SBA) bind to the surface of EDTA-dissociated cells from blastula and gastrula stage Xenopus laevis and X. mulleri embryos. 2. Binding of these lectins is abolished by appropriate haptens (alpha-methyl-D-mannopyranoside for F-conA and 2-acetamido-2-deoxy-D-galactose for F-sba). 3. Gastrula stage cells show a clustering or capping of lectin binding sites not shown by blastula stage cells. 4. At least for F-conA, this capping is induced by the lectin. 5. There are no striking regional differences in either amount or pattern of lectin binding in early gastrulae of both species.