Females and males of Lygus lineolaris, L. elisus, and L. hesperus were aerated separately and the major trapped volatiles were chemically identified. For L. lineolaris, extracts of the metathoracic scent gland were prepared by sex and chemically analyzed. In L. lineolaris and L. elisus airborne samples, hexyl and (E)-2-hexenyl butyrates occurred in female-derived samples in equivalent amounts, but the saturated ester was relatively much more abundant in male-derived samples. Lygus hesperus airborne samples were not sexually dimorphic; hexybutyrate occurred at much higher concentrations than did hexenyl butyrate in both female- and male-derived samples. Scent gland extracts of L. lineolaris showed the same ester pattern by gas chromatography is air borne extracts, but earlier eluting components differed quantitatively. The literature relevant to mirid sex pheromones is reviewed and discussed using the pheromone systems of the Pentatomidae for comparisons.