Arbovirus studies undertaken in Newfoundland between 1980-83 have resulted in the isolation of three California (CAL) serogroup viruses including an isolate of Jamestown Canyon (JC) virus from a mixed pool of Aedes abserratus and Ae. Punctor and two isolates of snowshoe hare (SSH) virus from pools of Ae. canadensis. Serological studies on human and animal sera have confirmed the circulation of SSH and JC viruses in Newfoundland with CAL serogroup hemagglutination inhibition antibody rates of 8.6%, 20.9% and 54.5% in 550 human, 43 horse and 11 snowshoe hare (Lepus americanus) sera, respectively.