Juvenile Hormone epoxidhydrolase (JHEH) is a key enzyme that controls the biological activity of JH. JHEH and JH esterase (JHE) degrade JH into JH diol and JH diol acid, respectively inactivating the hormone and terminating its biological activity. Three JHEH genes of Drosophila melanogaster including their promoter regions were cloned and sequenced. The promoter regions of the three genes were assayed for functionality by cloning them in pCaSpeR-AUG-gal plasmid containing the LacZ gene and the plasmid was expressed in D. melanogaster-2 cells. The three promoter regions were sequentially truncated to identify regions that bind inhibitors and activators. Using this approach, we identified a region that binds a transcription factor (TF) that activates the promoter. Knocking down the TF in the cells using dsRNA inhibited the activity of the JHEH promoter. The activity of the JHEH promoter was also assayed in the presence of JH III, JH II acid, 20 OH-ecdysone and its analogue tebufenozide. These results and the physiological role of the JHEH promoter in the control of JH III degradation in dipterans will be discussed.