Four birnaviruses isolated from fishes in Taiwan were compared to the three known serogroups of infectious pancreatic necrosis virus (IPNV) by neutralization tests and analyses of the virion polypeptides and RNA. Two viruses isolated from different populations of Japanese eels (Anguilla japonica) in the Lukang (LKE) and Dan Sway (DSE) regions and another virus from tilapia (Tilapia mossambica) in the Lukang area (LKT) were closely related to the AB strain of IPNV. A fourth virus isolated from rainbow trout (Salmo gairdneri) in the Kukuan region (KRBT) was similar to VR-299 IPNV. This indicates that North American and European serotypes of IPNV have been introduced to Taiwan. These studies represent the first complete characterizations of birnaviruses isolated from fish in Taiwan.