A series of laboratory tests were conducted in Northeast Louisiana during 1998 and 1999, to evaluate the efficacy of thiodicarb (Larvin 3.2F), spinosad (Tracer 4SC), and indoxacarb (Steward 1.25SC) against the soybean looper, Pseudoplusia inlcudens (Walker), on conventional cotton (cv. DP 5415) and transgenic Bacillus thuringiensis (Bt) (Berliner) cotton (cv. NuCOTN 33B). Plots within each variety received an application of either thiodicarb at 0.125, 0.25, 0.375, 0.5 lb AI/acre; spinosad at 0.012, 0.025, 0.037, 0.05 lb AI/acre; indoxacarb at 0.05, 0.07, 0.09, 0.11 lb AI/acre; or remained untreated. Foliage from each cultivar was placed into a 9.9 cm Petri dish along with three soybean looper larvae (L3 stage; 20 to 30 mg) within 1 hour after treatment (HAT). Larval mortality was rated at 72 hours after infestation (HAI). All rates of thiodicarb and all rates of spinosad (except 0.037 and 0.05 lb AI/acre) caused greater mortality when larvae were placed on treated foliage of NuCOTN 33B compared to DP 5415. Indoxacarb toxicity was not influenced by the two crop hosts. All rates of indoxacarb provided similar levels of soybean looper mortality on NuCOTN 33B and DP 5415.