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 of Muscovy duck or goose origin, as well as in Vero cells. In experimental infections, the dominant features of the disease were reproduced in day-old and young goslings. The biological and partial molecular characterisation of one of the isolated strains (D15/99) showed that it was related to the reovirus described as the cause of a similar disease of Muscovy ducks. An RT-PCR method suitable for the detection of reoviruses was also elaborated and tested. This is the first report on the involvement of reovirus in arthritis of geese.