A virus (SGV) was isolated from sand goby Oxyeleotris marrnoratus with ulcer disease reared in freshwater cages in Thailand. The virus was typical of members of the aquatic birnaviruses but it possessed phenotypic, serological and biochemical properties that distinguished it from previously described viruses of the Bimaviridae. Serologically, the virus is distinct from the described strains of infectious pancreatic necrosis virus (IPNV) and possesses the capability of replicating in several cell lines from warm water fishes at 30 'C. The use of rapid double-stranded RNA analyses and the immunoprecipltation of radio-labeled virion polypeptides demonstrated the unique biochemical nature of SGV and established the value of these techniques for strain identification of birnaviruses.