Galectins are beta-galactoside-binding proteins that occur intra- and extracellularly in many animal tissues. They have been proposed to form networks of glycoconjugates on the cell surface, where they may modulate various cell response pathways such as growth, activation and adhesion. The high resolution X-ray crystallographic analyses of three crystal forms of bovine galectin-1 in complex with biantennary saccharides of N-acetyllactosamine type reveal infinite chains of lectin dimers cross-linked through N-acetyllactosamine units located at the end of the oligosaccharide antenna. The oligosaccharide adopts a different low energy conformation in each of the three crystal forms.