Ten strains of Johnston Atoll (JA) virus were isolated from Ornithodoros capensis collected in a Gannet (Sula bassana serrator) colony in New Zealand. Its sensitivity to ether and sodium deoxycholate were confirmed and it was shown to have an RNA genome. It multiplied in day-old chicks but, unlike the prototype virus, it was not pathogenic for them. Transmission experiments and the high incidence of birds with neutralizing antibody indicate that the virus is maintained in the colony by a cycle involving ticks and Gannets. This is the first recorded tickborne arbovirus in New Zealand and extends the known range of JA virus from the tropics into the temperate zone.