In 1970—1971, a study of bats and their ectoparasites was carried out in the northern part of the Kirghiz S.S.R. on the shores of Issyk-Kul Lake. From 432 bats studied, 7 antigenically similar virus strains were recovered. Issyk-Kul (IK) virus belongs to the family Bunyaviridae.1 In 1966, Keterah virus, antigenically closely related to IK virus, was isolated by Marchette and Rudnick from A. pusillus ticks infesting Scotophilus temmenckii in Keterah, Kelantan, Malaysia. Issyk-Kul virus has been shown to be a member of the family Bunyaviridae on the basis of electron microscopic morphology. Intracranial inoculation of suckling mice proved to be the most useful method for virus isolation. No clinical disease has been described in domestic animals. Nevertheless, on the basis of serological surveys, domestic animals are involved in virus infection cycles. Human cases were reported only in adults. Disease was associated with presence of bats in houses, mainly Vespertiliopipistrellus and V. murinus.