A three-year investigation of the seasonal abundance and parity of mosquitoes at a high and low prevalence area for La Crosse (LAC) encephalitis in eastern Tennessee was conducted. We identified a high LAC prevalence site from which two recent cases of LAC encephalitis were confirmed, and an ecologically similar low prevalence site with no confirmed LAC cases. At both sites, mosquitoes were collected for twenty-four hours once a week between late May and early November 2003-2005. Mosquitoes were collected at each site using 2 CDC miniature light traps baited with carbon dioxide, 2 gravid traps, 1 omni-directional Fay trap baited with carbon dioxide and 25 oviposition traps. Stegomyia albopicta (Skuse), Ochlerotatus triseriatus (Say), and Aedes vexans (Meigen) were the most commonly collected mosquitoes at both sites. The first collection of Ochlerotatus japonicus (Theobald) in Tennessee occurred at the high prevalence site in 2003. Oc. japonicus has since been collected in several other counties in eastern Tennessee. Monthly parity rates for St. albopicta ranged from 0.08-0.77 at the high prevalence site and 0.00-0.75 at the low prevalence site. Monthly parity rates for Oc. triseriatus ranged from 0.10-0.64 at the high prevalence site and 0.05-0.80 at the low prevalence site. Parity rates changed during the summer in a roughly parallel manner for the two species. The carbon dioxide baited CDC light traps collected most of the adult mosquitoes used in parity determination.