The article presents information on the infectious pancreatic necrosis virus. Infectious pancreatic necrosis (IPN) is a viral infection primarily of salmonids, although IPN and IPN-like viruses have been isolated from non-salmonid fishes and marine invertebrates. In salmonids, acute infection occurs in fry and fingerlings and can cause high mortality. Subclinical or in apparent infection can occur in fish 6 months old or older, but mortality seldom results. Although epizootics have been reported throughout the world, some areas are at present apparently free of IPN.