Since the commercialization of Bt maize in 1996, the global area planted to maize or cotton varieties expressing Cry proteins derived from Bacillus thuringiensis (Bt) has steadily increased and reached a total of more than 42 million hectares in 20071. Several crops expressing novel insecticidal proteins derived from Bt or other sources are currently under development and will be commercialized in the near future.Similar to conventional agricultural pest control technologies, one risk associated with growing insect-resistant, genetically modified (IRGM) crops is their potential to adversely affect non-target organisms, which include a range of arthropod species that fulfill important ecological functions such as biological control. The potential for adverse effects of IRGM crops on non-target arthropods (NTAs) thus has to be evaluated as part of the environmental risk assessment (ERA) process that takes place prior to the decision to cultivate these crops commercially. The relative novelty of GM crops and the complexity of ERA procedures present regulatory authorities with a challenge in developing appropriate risk assessment methodologies. This is a particularly difficult task in the developing world, where regulatory infrastructure is still being established.