The four components of the synthesised sex pheromone of Spodoptera littoralis (Boisd.) are tetradecan-1-yl acetate (I); cis-9-tetradecen-1-yl acetate (IIA); trans-11-tetradecen-1-yl acetate (IIB); and cis-9, trans-11-tetradecadien-1-yl acetate (III). Dissolved in hexane they were dispensed in small polythene containers either singly or in combination over water-trough (WT) traps located in the potato-growing region of south-east Cyprus. Only III was necessary to attract male moths. Increased loadings of III resulted in an increased catch during the 20-day test periods; at a loading of 500 μg per dispenser the material was attractive for approximately 20 days, and at 5000 μg for up to 40 days. IIA combined with III in WT traps or with virgin females in the vane traps markedly reduced the catch of male moths. The level of inhibition induced by IIA on the attraction of female moths was related to the loading of this substance in the dispensers. An inhibitory effect on the attraction of female moths in vane traps was also shown for cis-11-tetradecen-1-yl acetate, although this substance was less active compared with IIA at the same loading. No marked attraction or inhibition was shown for I or IIB, neither was any synergistic action demonstrated for these substances when in combination with III. When 200 polythene dispensers each containing 500 μg of III were evenly distributed throughout a potato field of 2000 m2 during the test period of 19 days virtually no males were caught in a trap baited with virgin females located in the centre of the field. Using only 100 point sources of III at twice the loading, only a slight reduction in catch compared with control catches was noted.