Seven strains of a new Flavivirus, for which the name of Meaban virus is proposed, were isolated from the seabird tick Ornithodoros (A.) maritimus collected during 1981 and 1982 in nests of herring gulls (Larus argentatus) on islands of South Brittany, France. The new virus was compared serologically with 65 other flaviviruses including Tyuleniy virus and was found to be most closely related to, but different from Saumarez Reef virus, an agent previously isolated in Australia and Tasmania. Some general properties of Meaban virus are described and its antigenic relationships with other tick-borne flaviviruses associated with seabirds are discussed.