The effectiveness of boric acid (1%) and fipronil (0.1%) bait stations in reducing the number of laboratory-reared female Aedes aegypti and Ochlerotatus taeniorhynchus mosquitoes released in outdoor screened cages was evaluated. Both toxicants significantly reduced landing rates of the 2 mosquito species on a human subject. However, no significant reduction in the number of adult mosquitoes caught by counterflow geometry (CFG) traps baited with CO2 was observed in the boric acid- and fipronil-treated cages compared with control cage. The 2 bait stations were further evaluated against natural populations of adult mosquitoes in 3 residential yards (each ca. 0.8 ha) in St. Johns County, FL. Both bait stations failed to significantly reduce counts of female mosquitoes landing on a human subject; and the capture rates of adult mosquitoes by CFG traps baited with dry ice in bait-treated and control experimental yards were not significantly different. Further field research is needed on the density and placement of bait stations in order to determine their utility in adult mosquito control programs.