An attempt will be made to survey the recent literature which reports the identification of "endogenous lectins", carbohydrate-binding proteins, in a variety of vertebrate tissues. The function of lectins from cellular slime molds, plants and various microorganisms will be briefly reviewed. The paucity of functional information concerning lectins from vertebrate tissues will allow speculation on possible functions which relate to intercellular and intracellular recognition processes in development, by analogy to work done in simpler systems. Comparisons of the chemical and physical properties of these interesting vertebrate lectins will be made. We will also review studies from our laboratory which concern a developmentally regulated carbohydrate-binding protein in mammalian brain.