Field and laboratory studies were conducted in 1998 and 1999 to evaluate efficacy of new and standard insecticides for control of tarnished plant bug (Lygus lineolaris (Palisot de Beauvois)) in cotton. Results from tests with Orthene (acephate), Regent (fipronil), Bidrin (dicrotophos), Leverage (imidacloprid + cyfluthrin), Actara (thiamethoxam), Provado (imidacloprid) and Steward (indoxacarb) evaluated in small plot trials are presented as well as results from cage studies. It was apparent in cage trials that 3 days was not sufficient time to evaluate some of the newer insecticides such as Steward, and evaluation times for mortality determinations after treatment were lengthened from 3 to 4 days. In the laboratory studies using a waterfoam bioassy method, toxicity of Actara , Provado and Steward was examined, and LC₅₀ values for the formulated insecticides were 0.08 ppm, 0.69 ppm, and 1.46 ppm for Actara, Provado and Steward, respectively. The slow action of these compounds in the laboratory required that the bioassays be extended to 96 hrs. supporting the practice of extending the evaluation interval in field cage studies to 4 days after treatment.