The discovery of the soybean aphid, Aphis glycines Matsumura, in U.S. soybean production systems in 2000 has provided a unique opportunity to study the interaction of a new invader with existing natural enemy communities. One research thrust has been examining the role of predators in soybean aphid dynamics in the Midwest. We discuss the roles of predatory arthropods in field crops and set forth a conceptual model that we have followed to identify key predators in the soybean aphid system. We identify Orius insidiosus (Say) and Harmonia axyridis (Pallas) as potentially key predators and show our findings on their phenology in soybean fields and their impact on soybean aphid population dynamics. Finally, we discuss how this information can be used in integrated pest management programs for soybean aphid and point to gaps in our knowledge where future studies are needed.