Ochlerotatus j. japonicus, a recent introduction to the United States, was studied to determine its capability to serve as a vector of La Crosse (LAC) virus. A field-collected population of Ochlerotatus triseriatus, the primary vector of LAC virus, was similarly tested for comparison. After Oc. j. japonicus ingested virus from hamsters with viremias of 10^3.6–5.4 plaque-forming units (PFU)/ml of blood, its estimated transmission rates were 35–88%. These rates were slightly lower than, though similar to, those for Oc. triseriatus, 75–100%. Viral titers in Oc. j. japonicus peaked at ≈10^5.5 PFU/mosquito about 7 d after ingesting a blood meal in which the concentration of LAC virus was 10^5.4 PFU/ml of blood; virus had disseminated from the midgut in 100% (8/8) of these specimens. These data, combined with the close association between the habitats of Oc. j. japonicus and Oc. triseriatus and the reported expansion of the range of this newly discovered species in the eastern United States, indicate that Oc. j. japonicus could function as an additional vector of LAC virus.