Large-scale implementation of transgenic crop varieties raises concerns about possible non-target effects on other organisms. This study examines a potential mechanism by which genetically modified plants may affect the population dynamics of arthropods associated with them. Herbivore-induced volatile emissions from Bt maize plants were compared to those from a non-transformed isoline after exposure to various types of leaf damage. When equal numbers of Helicoverpa zea Boddie (Lepidoptera: Noctuidae) larvae fed on Bt and non-Bt maize, volatile emissions were greatly reduced in the transgenic plants, which exhibited reduced leaf damage. When damage levels were controlled by adding additional larvae to Bt plants, the plants’ volatile emissions increased but displayed significant differences from those of non-transgenic plants. By the third day of feeding, significantly higher amounts of linalool, myrcene, and geranyl acetate were released from transgenic maize than from non-Bt plants. Because individual larvae fed less on Bt-plants producing a different damage pattern, we controlled the duration of feeding by individual larvae. This produced similar volatile profiles in Bt and non-Bt plants. Simulating herbivore damage by mechanically damaging leaves and applying regurgitant standardized damage even further and also resulted in similar emission patterns between Bt and non-Bt maize. These results provide new insight into the possible effects and consequences of transgenic plants on the chemical ecology of agroecosystems.