Global atmospheric carbon dioxide concentration [CO₂] increased 20% in the last century and is expected to increase another 48% by 2050. Surface concentrations of ozone [O₃] also are increasing rapidly in agricultural areas of the northern hemisphere and are expected to increase another 20% by 2050. To better understand the combined impact of increased [CO₂] and [O₃] on crop production in the Midwest, we used a 32-ha experimental field planted with soybean (Glycines max L. Merr.). The field included sixteen 21.3-m-diameter plots using free air gas concentration enrichment (FACE) to simulate the changes in atmospheric composition forecast for 2050. We evaluated the impact of elevated [CO₂] and [O₃] singly and in combination on adult and egg densities of the variant western corn rootworm, Diabrotica virgifera virgifera LeConte. During 2003–2004, each of the four blocks included four plots, representing the four treatments (ambient atmospheric control, elevated [O₃], elevated [CO₂], and an elevated [CO₂] and [O₃] combination). Although elevated [CO₂] and [O₃] did not have an effect on adult female densities of the variant western corn rootworm, they did significantly affect egg densities. Approximately twice as many eggs were found in the soil of soybean plots exposed to elevated [CO₂] compared with ambient control plots or those with elevated [O₃]. Egg densities were even greater (approximately three times) in plots with the elevated [CO₂] and [O₃] combination treatment than in ambient plots. This suggests that rising [CO₂] and [O₃] are stimulating egg-laying by the variant western corn rootworm, potentially increasing population densities and risk of damage to the subsequent corn crop.