Snowshoe hare (SSH) virus was isolated from 6 of 10,188 unengorged female mosquitoes of 4 species, including 3 of 7017 Aedes communis and 3 of 2088 Ae. Nigripes collected throughout the boreal forest of the Yukon Territory between 3 June and 22 July 1981. During 10 summers from 1972 to 1981, 48 SSH and 4 Northway virus strains have been isolated from 125,442 mosquitoes of 7 species collected in the western Canadian Arctic. Plaque reduction neutralization tests revealed close antigenic relationships between strains of SSH virus isolated during 8 of 10 years.