In response to a growing, human suburban population and an escalating problem of used tire disposal, a summer-long survey of discarded tires and their associated mosquitoes was conducted in northeastern Illinois in 1985. Within a 291 km2 area, a monthly average of 7,823 tires were distributed among 127 sources classified into 7 categories: fields/ditches (25% of total sources); salvage yards (7%); trucking/construction companies (13%); woodlots (15%); school playgrounds (11%); service stations (16%); and tire dealers (11%). Distribution and abundance of each source category appeared to reflect local land usage and extent of urbanization. Wooded sites surpassed service stations, dealers, and salvage yards in the average percentage of flooded tires (86% vs. 25% ea.) and percentage of those larval-infested (58% vs. 25% ea.). Overall, 6,398 mosquito larvae among 9 species were collected with Culex restuans (82%) and Cx. pipiens (13%) predominating. Species segregations with respect to the tire source are revealed. Possible control strategies of mosquitoes in tires are summarized.