Lygus hesperus, the western tarnished plant bug, feeds on a variety of economically important crops where they can cause severe damage. A synthetic attractant for monitoring or mass trapping Lygus would be a useful addition to current IPM programs. We previously demonstrated that feeding damage by L. hesperus to alfalfa (a preferred host) induces a plant volatile response, which in turn increased attraction of L. hesperus to plants. The volatile profiles of alfalfa also depended on time of day and plant phenology; and in general included a mixture of lipoxygenase products (predominantly GLVs), terpenes, and flower specific compounds. Individual or mixtures of these alfalfa volatiles may be useful as attractants. Here we present results of behavioral assays using a Y-tube olfactometer that examined the response of adult L. hesperus to some of the major alfalfa profile components.