(E)-9-Tetradecenyl acetate had previously been shown to be present in extracts of the female European corn borer,Ostrinia nubilalis (Hübner), along with (E)-11-tetradecenyl acetate, (Z)-11-tetradecenyl acetate, and tetradecyl acetate. In field and laboratory assays (E)-9-tetradecenyl acetate suppressed male attraction and precopulatory behavior, but tetradecyl acetate had no influence. The bioassay data indicate that (E)-9-tetradecenyl acetate and the isomeric 11-tetradecenyl acetates are perceived through separate sensory channels. A blend of (E)-9-tetradecenyl acetate and the 11-tetradecenyl acetates might be useful as a disrupter of mating efficiency of this pest species in the field.Mention of a commercial or proprietary product in this paper does not constitute an endorsement of this product by the U.S. Department of Agriculture. The research work at UCLA was supported by a grant from the Mobil Foundation. The research is also a joint contribution: USDA and Journal Paper No. J-9103 of the Iowa Agricultural and Home Economics Experimental Station, Ames, Iowa 50011.