Brown stink bug, Euschistus servus (Say), has greatly increased in numbers in the Brazos Valley in Central Texas and in many other areas of the Cotton Belt, and has become a major pest of cotton, Gossypium hirsutum L., and other crops including pecans, Carya illinoensis (Wangenh.) K. Koch. Use of insecticides is among the most important of the limited control options available against this pest. Glass-vial bioassays were used to evaluate the toxicity of selected synthetic pyrethroid and organophosphate insecticides to adult brown stink bug captured in blacklight traps. A comparison was also made of toxicity of λ-cyhalothrin to brown stink bug collected directly from the field to those captured in blacklight traps. Lethal concentration value (LC₅₀) (upper and lower 95% confidence limits) for dicrotophos for 24-hour response, 0.30 (0.24–0.37) µg per vial, was significantly less compared to acephate with an LC₅₀ of 1.38 (1.01–1.81) µg per vial and chlorpyrifos with an LC₅₀ of 5.00 (4.27–5.67) µg per vial. Dicrotophos was five- and 17-fold more toxic to brown stink bug than acephate and chlorpyrifos, respectively. The order of toxicity to brown stink bug for synthetic pyrethroids was: bifenthrin = zeta-cypermethrin = γ-cyhalothrin > λ-cyhalothrin > cypermethrin. LC₅₀ values ranged from 0.27 (0.18–0.51) for bifenthrin to 1.35 (1.01–1.90) µg per vial for cypermethrin, a five-fold difference. LC₅₀ values for brown stink bugs collected from the field or captured in blacklight traps were not significantly different which suggests that brown stink bugs captured in blacklight traps may be used for insecticide bioassays. Data presented are useful for selecting insecticides for control and establishing baselines to monitor development of resistance of brown stink bugs to insecticides in the Brazos Valley of Central Texas.