One strain of a Cache Valley like virus (Bunyamwera serogroup) was recovered from 204,753 female mosquitoes representing 36 species collected and tested in Connecticut from 1969 through 1980. This isolate, identified by complement-fixation and suckling mouse neutralization tests, was from a pool of 22 Aedes triseriatus collected in light traps during September 1979. Virus was not detected in 431 adult male or 8,317 immature Ae. triseriatus from the same area. Neutralizing antibody against this virus was demonstrated in 7 of 49 deer sera from Connecticut, but not in a small number of sera from cottontails, chipmunks, and squirrels from the same area. This isolate extends the recognized geographic range of the Bunyamwera group into New England and it is the first Cache Valley like strain reported from Ae. triseriatus.