The cDNAs of Drosophila melanogaster and Aedes aegypti juvenile hormone epoxide hydrolases (JHEH) have been cloned and sequenced. The promoter regions of the three Drosophila genes were sequenced, cloned and characterized for promoters’ activity and transcription factors in S2 cells. Several transcription factors binding sites were identified and mapped. The expression of these genes in Drosophila and mosquito was compared during adult development in the ovaries, fat-body, gut and the head-thorax using Northern blot analyses and RNA induced silencing . The results of these experiments will be discussed.