Pheromone washes from calling female moths of redbacked cutworm,Euxoa ochrogaster (Guenee), contained the following acetates that are structurally similar to those of known lepidopteran pheromones (%): decanyl (8.7), dodecanyl (8.5), (E)-5-dodecenyl (3.3), (Z)-5-dodecenyl (76.4), (Z)-7-dodecenyl (3.1), and (Z)-9-dodecenyl (trace<0.5%). This is the first time that (Z)-5-dodecenyl acetate has been identified as a pheromone component. Three types of specific receptor cells were found in the male antennae, and they responded to (Z)-5-decenyl acetate, (Z)-5- and (Z)-7-dodecenyl acetates, respectively. Strong electroantennographic detector responses were also recorded for these three acetates and for (Z)-5-undecenyl acetate. The evidence for the presence of (Z)-5-decenyl acetate in the pheromone washes was inconclusive. The presence of (Z)-7- and the absence of (Z)-8-dodecenyl acetates were confirmed by a special electroantennographic detector technique in which the detector antennae were from males of other species that were known to have strong responses to these acetates. This is a very useful technique. Field results show that low concentrations (0.1–1.3%) of (Z)-5-decenyl acetate were synergistic when tested in a previously reported blend, but 6% was inhibitory. Similarly, (Z)-7-dodecenyl acetate at 2% or less may be essential for the attraction of males, but in previous tests at 14% it also was inhibitory. Species-specific attractant blends for redbacked cutworm males are described.