Different formulation of the synthetic female sex pheromone of Spodoptera littoralis were evaluated in the field. A trap baited with 1 mg of cis-9, trans-11-tetradecadienyl acetate (72% active isomer) alone adsorbed in a rubber septum was equivalent in effectiveness to a trap baited with virgin females for at least 77 days. The purified attractant (92% active isomer), however, was significantly less efficient in attractiveness than the partially purified synthetic attractant (72% active isomer). The addition of a small amount of cis-9, trans-12-tetradecadienyl acetate to the purified attractant strongly enhanced te attraction. However, cis-9, trans-12-tetradecadienyl acetate had no synergistic effect when added to the partially purified attractant. The addition of increased amounts of cis-9, trans-12-tetradecadienty acetate markedly reduced the cathch of male moths. The combination of 4.8-mg attractant (97% purity) with 12-mg antioxidant adsorbed on a filter paper was somewhat less efficient in attractiveness than virgin females.