The galectins constitute a large family of carbohydrate-binding proteins that function in many systems both intracellularly and following secretion. Galectins contain either one or two carbohydrate recognition domains (CRR) which mediate recognition of N-acetyl-lactosamine-containing glycoproteins. Some galectins exist in multiple isoforms due to alternative splicing. Individual galectins differ in their tissue distribution and in their carbohydrate-binding specificities.