The sex attractant of Pectinophora gossypiella (Saunders) was isolated from mixed sexes and from females only by chromatographic purification of the alcohol precursor and its acetylated product. Studies on the structure of the pheromone confirm a previous report that it is a mixture of (Z, Z)- and (Z, E)-7, 11-hexadecadien-1-ol acetate in roughly equal amount. All 4 geometric isomers of 7, 11-hexadecadien-1-ol acetate were synthesized and characterized. Electroantennogram response was determined for the 4 isomers and hexalure. Moth captures in traps were determined for the following: the 4 isomers individually and all together; 2-component mixtures of the isomers; the 1:1 mixture of the pheromonal isomers plus small amounts of the other 2 isomers; a series of concentrations of the pheromone (1:1 isomer ratio) with and without trioctanoin as keeper; and the pheromone plus candidate inhibitors (which were found in the extract), synergists, and a stabilizer.