The efficacy of four formulations of Fipronil (80 WG, 2.5 EC, 0.73 EC, and 2.5 Gel) at three rates (0.018, 0.025, and 0.038 lb AI/acre) and Vydate (3.77 L at 0.25 lb AI/acre) for tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois) and boll weevils, Anthonomus grandis Boheman, was determined by caging adults of the two species on cotton terminals treated in a spray chamber with the insecticides. All formulations and rates of Fipronil and Vydate were effective against boll weevils producing mortalities of 90% or greater. Fipronil 80 WG and 2.5 EC were the best formulations for plant bug control producing mortalities at rates of 0.025 and 0.038 lb AI/acre that were not significantly different from mortality obtained with Vydate. Two or three applications of Fipronil 80 WG (0.05 lb AI/acre), Fipronil 2.5 EC (0.05 lb AI/acre), Provado 1.6 F (0.047 lb AI/acre) and Curacron 8 E (0.5 lb AI/acre) were needed to control a large insecticide resistant population of plant bugs found in cotton in August. The effectiveness of Fipronil and Provado on plant bugs, along with the fact that each represents a new class of insecticide, will be very useful in early season insect control and in reducing insecticide resistance.