Host-feeding associations of mosquitoes were determined by exposing 20 species of woodland vertebrates to natural mosquito populations. Only Culex pipiens (L.) and C. restuans (Theobald) showed a definite host preference to the avian hosts. However, C. pipiens fed also on several of the mammal hosts. Aedes and Psorophora showed a preference for mammal hosts especially nonrodents. Aedes vexans Meigen, A. stimulans group, and Psorophora ferox (Humboldt) exhibited little response to rodents or cold-blooded vertebrates. Aedes trivittatus (Coquillett); A. sticticus (Meigen); and Mansonia perturbans (Walker) were general feeders. Aedes canadensis (Theobald) had a high attraction and engorgement rate on turtles as well as on some mammals, while A. cincreus Meigen showed a strong association with chipmunks and ground squirrels. Of the 7 rodent hosts the 13-lined ground squirrel, Citellus tridecemlincatus (Metchill), was the most acceptable. Most of the Aedes mosquitoes appeared to attack the most available host in an area.