Three new insect growth regulators (IGRs) were tested against Culex, Aedes and Psorophora mosquitoes. In the laboratory the 3 IGRs were active in the range of 0.3 to 1.5 ppb against Cx. quinquefasciatus. In field tests, the IGRs fenoxycarb and S-31183 formulations yielded complete control of floodwater mosquitoes at the rates of 0.005 to 0.01 lb AI/acre. In field tests against Cx. tarsalis, S-31183 formulations produced complete inhibition of emergence at the rates of 0.005 to 0.025 lb AI/acre. Fenoxycarb formulation produced similar results at the rate of 0.1 lb AI/acre. It is possible that initial and residual field activity of both IGRs can be increased by employing suitable formulations.