The pathology, epizootiology and aetiology of a specific disease of young geese, which has been seen in Hungary for more than three decades, were investigated. The disease was characterised by splenitis and hepatitis with miliary necrotic foci during the acute phase, and epicarditis, arthritis and tenosynovitis during the subacute/chronic phase. Clinical signs usually appeared at 2 to 3 weeks of age and persisted for 3 to 6 weeks. From different organs of the affected birds, a reovirus was isolated in embryonated eggs and tissue cultures ofMuscovy duck or goose origin, as well as in Vero cells. In experimental infections, the dominant features of thedisease were reproduced in day-old and young goslings. The biological and partial molecular characterisation ofone of the isolated strains (D15/99) showed that it was related to the reovirus described as the cause of a similardisease of Muscovy ducks. An RT-PCR method suitable for the detection of reoviruses was also elaborated andtested. This is the first report on the involvement of reovirus in arthritis of geese.