In 1989, during a period when high mortaliites of turbot fry were recorded in several commercial farms, samples for virus detections were collected in 6 farms. Samples were also collected from two broodstock populations and egg batches from one farm, and from wild fauna in the surroundings of a second farm where infectious pancreatic necrosis virus (IPNV) was isolated from turbot fry with pronounced necrosis in exocrine pancreatic tissue. IPNV was isolated from fry collected in 3 of the farms, from invertebrate fauna and in a few samples from wild fish. Virus was not detected in broodstock or egg batches. The finding of IPNV in wild fish, in invertebrate fauna and in Artemia point to several potential virus sources and ways of transmission. Shortened abstract.