Serological studies for arboviruses were conducted on 725 animal sera collected in 22 Ontario townships between 1975 and 1980 including 44 coyote (Canis latrans), 277 red fox (Vulpes vulpes), 192 raccoon (Procyon lotor) and 212 striped skunk (Mephitis mephitis). Hemagglutination inhibition antibodies to two flaviviruses, namely St. Louis encephalitis and Powassan were found in 50% of coyote, 47% of skunk, 26% of fox and 10% of raccoon sera. Similarly, hemagglutination inhibition antibodies to a California serogroup virus, snowshoe hare, were found in 12% of fox, 7% of skunk, 7% of raccoon and 5% of coyote sera. No antibodies were detected to two alphavirus, namely eastern equine encephalitis and western equine encephalitis, antigens. This study affirms the endemic presence of Powassan and snowshoe hare virus and further delineates the scope of St. Louis encephalitis activity in Ontario.