Multivalent protein–carbohydrate interactions regulate essential cellular events, including cell proliferation, adhesion and death. These multivalent interactions can create homogeneous complexes of lectins, such as the galectins, with their saccharide ligands. Lectin–saccharide complexes can concentrate specific glycoproteins or glycolipids within the lattice, while excluding other cell surface molecules. The formation of lectin–saccharide lattices on the cell surface can thus organize the plasma membrane into specialized domains that perform unique functions. Multivalent galectins have the ability to form cross-linked lattices with glycoproteins on the cell surface. How does this process influence cell signaling, cell adhesion and cell death?