Female abdominal tip extracts of peach twig borer moths, Anarsia lineatella Zeller, from Washington and California were analyzed and found to contain trans-5-decenyl acetate as a pheromone component. There was also evidence for the presence of ca. 15% of the corresponding alcohol. These synthetic compounds proved to be very attractive to peach twig borer males in field studies in both states through a range of ratios.