Invertebrate immune system must rely on non-self-recognition molecules to ensure efficient defence responses against infectious pathogens that continuously threaten their survival. Lectins from the hemolymph of invertebrates, including crustaceans, have been regarded as potential molecules involved in immune recognition and microorganism phagocytosis through opsonization. This report presents an overview on the molecular characterisation, physiological role, synthesis and induction upon infection of arthropod lectins, with special emphasis on crustaceans. Although the participation of arthropod lectins in immune surveillance is not fully demonstrated, some recent reports in insects and horseshoe crabs appear to support this concept more convincingly. Unfortunately, such unambiguous evidences have not been thus far demonstrated in crustaceans. The results obtained in related arthropod groups could, however, be predictable for crustaceans. The precise mechanisms underlying non-self-recognition represent the basis to prevent and control infections as well as to stimulate animal resistance. This is particularly relevant for cultivated aquatic species, especially penaeid shrimps, which are frequently constrained by recurrent diseases that often provoke great economic losses. q 2000 Elsevier Science B.V. All rights reserved.