In the context of infectious diseases in mollusc and shrimp aquaculture, research must be focused on diagnosis for zoosanitary controls but also on obtaining resistant animals. This last strategy depends heavily on the development of knowledge about marine invertebrate immunology. With the establishment of purification protocols for the main invertebrate pathogens, progress has been made in the study of host-pathogen interactions at cellular and molecular levels and in identifying immune effectors involved in the destruction of pathogens. Recent information on molluscs and crustaceans is presented, concerning both hemocyte studies and cellular defence functions and humoral effectors, with special reference to their application to selection of pathogen-resistant animals. With this aim, research prospects will essentially be devoted to the identification and characterization of immune genes, either specific or heterologous, which could be candidates for mollusc and shrimp genetic transformation. © 1995.