Abstract
Cross-neutralization studies on 42 flaviviruses and their respective antisera were performed by a plaque assay in a line of pig kidney cells. Six tick-borne viruses fell into one subgroup; seven viruses associated with bats and small rodents and a further tick-borne virus fell into a second subgroup. Twenty-two mosquito-borne viruses fell into one major and four minor subgroups. Four mosquito-borne, one tick-borne and one bat virus showed no relationship to any other flavivirus.