Abstract. In addition to the pheromone components (Z)‐5‐decenyl, (Z)‐7‐dodecenyl and (Z)‐9‐tetradecenyl acetate (Z5‐10:OAc, Z7‐12:OAc and Z9‐14:OAc), it has previously been shown that the sex pheromone gland of the turnip moth, Agrotis segetum (Lepidoptera: Noctuidae Schiff) contains 10:OAc, 12:OAc, Z5‐12:OAc, Z9‐12:OAc, 11–12:OAc, Z5‐14:OAc, Z7‐14:OAc and Z11‐16:OAc. To find out whether any of these additional compounds is involved in the sex pheromone communication in A. segetum, a comprehensive electro‐physiological and behavioural investigation was conducted. Single‐sensillum recordings on male antennae revealed three subtypes of sensilla among the previously so‐called Z5‐10:OAc sensilla. One subtype was identified having one receptor neurone (A) that responded to Z5‐10:OAc with a large spike amplitude and another neurone (B) that responded to (Z)‐5‐decenol (Z5‐10:OH) with a small spike amplitude. In another subtype the B neurone responded to Z5‐12:OAc and sometimes also to 27‐12:OAc and 10:OAc, in addition to responding to Z5‐10:OH. In a third subtype the A neurone responded to all acetates identified from the female pheromone gland, whereas the small spike amplitude neurone was tuned to Z5‐10:OH. A flight tunnel assay showed that blends composed of nine, eight or seven compounds were equivalent to the previously identified three‐component pheromone blend in eliciting male behavioural responses. In field trapping tests, blends of eleven, nine or seven compounds did, however, catch significantly more moths than the three‐component blend. Further assays showed that only 25‐ 12:OAc could significantly increase the catch numbers when added to the three‐component blend, and thus qualified as a fourth pheromone component in A. segerum. The behavioural significance of additional female‐produced acetates — for which males possess antennal receptors — is suggested, but may be impossible to confirm because of ‘diminishing returns’ when trying to refine a multicomponent pheromone further.