A virus, which is morphologically identical and antigenically related to two previously known isolates of infectious bursal disease (IBD) virus, was isolated from pooled faeces of 6-week-old turkeys with diarrhoea. It is concluded that this virus, designated TY89, is an isolate of IBD virus. The isolation of TY89 was heavily dependent upon the use of electron microscopy and the immunofluorescence technique. Antibody to TY89 virus was detected by both indirect immunofluorescence and serum neutralisation tests in 28 of 95 (29%) sera collected from 20-week-old turkeys. The available evidence suggests that this virus has only recently been introduced into turkeys in Northern Ireland. It is believed that this is the first report of natural infection of turkeys with IBD virus.