Snowshoe hare (SSH) virus (California encephalitis group) was isolated from 7 of 162 pools comprising 7472 unengorged adult female mosquitoes of 3 species which were collected throughout the Yukon Territory between 9 June and 30 July 1980. All isolates were achieved from Aedes communis mosquitoes, with isolations ranging from 1:78 to 1:483 mosquitoes collected at southern Yukon locations (61 N) and 1:182 to 1:382 at northern Yukon locations (66 N, 137 to 138 W) along the recently constructed Dempster Highway.