Limited laboratory and field studies have indicated that the insect growth regulator (IGR)novaluron exhibits good activity against larvae of pest species in the orders Coleopteia, Hemiptera (suborderHeteroptera), and Lepidoptera by both ingestion and contact. We completed laboratory and field studies toevaluate activity and efficacy of novaluron against Culex mosquitoes. In laboratory studies, novaluron was highlyactive against Cx. quinquefasciatus, as indicated by low levels of inhibition of emergency (IE), at the 50% level,IE50 (0.159 ppb for 2nd-stage larvae and 0.118 ppb for 4th-stage larvae) and IE90, at the 90% level, (0.604 ppbfor 2nd-stage larvae and 0.595 ppb for 4th-stage larvae)...