Insect-resistant transgenic Bt cotton has, in general, increased yield and reduced insecticide use in cotton production by successfully managing primary pests. However Bt cotton has not eliminated all pest problems. In the southeast US, outbreaks of stink bugs on Bt cotton have become increasingly serious, requiring more insecticide sprays. Such outbreaks represent significant risks in their potential to erode the economic and ecological benefits of Bt cotton. Understanding the ecological mechanisms driving stink bug outbreaks can improve attempts to predict outbreaks in countries considering the commercialization of Bt cotton. Though insecticide release is likely an important factor in stink bug outbreaks, we hypothesize that two ecological mechanisms influence stink bug outbreaks: 1) release from competition with primary pests and 2) changes in stink bug feeding behavior due to physiological or nutritional changes in the plant. In this talk, we will present results from experiments and outline future work designed to test these hypotheses. We will also describe how this work could be used as a case study to improve ecological risk analyses of transgenic crops.