A total of 20 virus strains were isolated from arthropods and rodents in the Baikal region in 1992. Thirteen of these were California serogroup viruses, 4 Batai virus strains (Bunyaviridae, Bunyavirus), and 3 Gheta virus strains (Togaviridae, Alphavirus, Semliki complex). The rates of mosquito infection with California, Batai, and Gheta viruses were 1:6500, 1:24000, and 1:24000, respectively. The results of the neutralization test indicate the similarity of the isolated California complex strains to the mountain hare virus, the most pathogenic virus in this group.