Field trials in Alabama, Georgia, and South Carolina determined the effect of transgenic Bollgard cotton and conventional varieties treated with insecticides on natural enemy populations. Initial results indicated that Bollgard had a lesser effect on arthropod natural enemy populations than did conventional, broad spectrum insecticides. The effects on nontarget populations, which depended on pest populations and agronomic practices, varied among regions and years. An accurate evaluation of the effect on natural enemy populations may require a multiyear study.