A laboratory experiment was conducted to test the western equine encephalomyelitis (WEE) virus transmission ability of Aedes hendersoni Cockerell, a species thought to be closely related to Aedes triseriatus (Say), which has been shown in laboratory studies to transmit WEE virus. Ae. hendersoni became infected at a rate of 100% following ingestion of blood from viremic baby chicks containing 109.8- 1011.3 suckling mouse LD50 of WWE virus. Thirteen days after ingestion of the infectious blood meal 56% of the mosquitoes were able to transmit the virus to normal baby chicks.