During July to December 1983 birds in 192 racing pigeon lofts were confirmed as infected with paramyxovirus type 1 virus on the basis of disease signs alone when contact with infected cases was known (10) or with supporting serology (130), virus isolation (eight) or both (44). These outbreaks were mainly concentrated in south Wales (89) and Dorset (40). In all, 29 counties of Great Britain were involved. In the majority of outbreaks (69 per cent) activities associated with racing were strongly implicated in the spread of the disease but trade in birds, stray bird contact, loft visits and contact at shows were also possible methods of spread. Although considerable variation was seen in the pathogenicity of the viruses isolated from affected birds there were no apparent epizootiological links between isolates of similar virulence.