The regions of the developing craniofacial skeleton and gut of Xenopus laevis have been confronted in vivo with purified embryonic galactoside-binding lectin or its hapten inhibitor thiodigalactoside (TDG). Confrontation was carried out at stage 24-26 (cranial neural crest migrating). Further development of the head skeleton and gut has been monitored in living animals and in histological cross-sections of selected head regions. Lectin treatment correlates with the development of larger heads than controls. TDG treatment correlates with the development of narrower heads than controls. After both treatments, head cartilages are composed of fewer total chondrocytes. Both neural crest and non-neural crest cartilages are affected. The gut forms larger, irregular coils after lectin or TDG confrontation. The results suggest that galactoside-binding lectin/galactoside-bearing receptor adhesive interactions are important in development of the craniofacial/visceral skeleton and gut.