Laboratory bioassays of cis-7-dodecenyl acetate, a natural sex attractant of the cabbage looper, Trichoplusia ni (Hübner), and several related unsaturated esters including the trans isomer of the attractant revealed that any change in structure resulted in a pronounced reduction in activity. There appeared to be a favored stereochemical relationship between the double bond and the carbonyl oxygen that was necessary for activity. The adults of Rachiplusia ou (Guenée), Pseudoplusia includens (Walker), and Autographa biloba (Stephens) were shown to possess or respond to the attractant.