In laboratory studies onCadra cautella(Walker) we found that a component of the female sex pheromone (S.P.) complex,cis-9,trans-12-tetradecadien-1-ol acetate (c9,t12-14C-Ac) was slightly more effective than its isomers as a mating inhibitor. Relatively large amounts of a mixture ofc9,t12-14C-Ac and an additional component of the S.P.,c9-14C-Ac, on filter paper or topically applied to males reduced mating. However, the extent of mating inhibition was never greater than 29% of control mating. Inhibition of the stimulatory response of maleC. cautellais readily attained by previous exposure to synthetic S.P. but this inhibition is not a reliable index of its effectiveness as a mating inhibitor.