A symposium entitled “Progress in fish and shellfish immunology and contribution to the fisheries” was held by the Japanese Society of Fish Pathology in Shimonoseki on 4th October, 2003. This was aimed to have an overview of the progress in fish and crustaceans immunology and its contribution to the development of aquaculture. The symposium was composed of six categories: (1) Prevention of infectious diseases of crustaceans by activation of immunodefense system, (2) Current status and prospects in fish immunology, (3) Immune relevant genes and their functions in fish, (4) Prevention of infectious diseases in fish by inducing cytokines, (5) Current status and prospects of development of fish vaccines, and (6) Potential application of recombinant cytokines and new gene ration vaccine for the control of infectious diseases in domestic animals. Outbreaks of infectious diseases, causing serious damage to cultured fish and shrimp, have been occurring in Japan. The advanced knowledge in fish and shellfish immunology will contribute to the control of infectious diseases in aquaculture.