Studies of arbovirus infections of snowshoe hares in central Alberta were carried out in 1961 through 1967, in an attempt to determine which arboviruses were importantly associated with the hare population. These studies were carried out during a period of marked decline of the hare population. Neutralizing antibodies to California encephalitis virus and Silverwater virus were present in the population throughout the study with prevalence ranging from 59% to 97% and from 0% to 68%, respectively. Antibody prevalence rates to western equine encephalomyelitis virus were generally low except for two epizootics during the spring and early summers of 1963 and 1965, when rates of over 80% were observed. The significance of these findings is discussed. Data are presented which show a rapid, significant decline in neutralizing antibody prevalence which suggests that hares convalescent from these arbovirus infections experienced higher mortality than did uninfected animals.