Technical Abstract: Bollworm, Helicoverpa zea (Boddie), larvae are known to move away from Bollgard cotton terminals. Bollworm larvae are also found more frequently on flower buds (squares) and bolls of Bollgard as compared to those of non-transgenic cotton. However, data are not available for bollworm behavior on commercially available transgenic cotton varieties expressing two Bacillus thuringiensis Berliner proteins. Thus, field studies were conducted in Stoneville, MS, during 2007 and 2008 to determine whether bollworm behavior differed between cotton expressing the Cry1Ac and Cry1F proteins (Widestrike, Phytogen 485) and non-Bt cotton (Phytogen 425). Two-day-old bollworm larvae were placed into terminals of either individual cotton plants or plants within 1-m plots during the flowering period. Comparison of larval movement away from cotton terminals between Widestrike and non-Bt plants did not differ at 3, 6, 24, or 48 h after infestation. In addition, larval distribution on fruiting structures did not differ between Widestrike and non-Bt cotton. These data indicated that different scouting methods for bollworm larvae should be used for the various Bt cotton technologies commercially available.