Transgenic Bacillus thuringiensis (Bt) corn expressing toxins against various target pests is now grown on approximately 20 million acres in the US. However, its potential effects on the soil ecosystem remain poorly understood. It is important to investigate how the introduction of transgenic plants will influence soil decomposition processes because the decomposer food web plays a critical role in determining the mineralization of nutrients in soil, plant nutrient acquisition and plant productivity. In a two-year study we investigated the impact of Bt corn on the carabid population using pitfall traps. Preliminary results indicate that there are some substantial differences in the community structure in Bt versus non-Bt corn. In another study we determined 1) how long the toxin persists in plant residue remaining in the field after harvest and 2) which species in the soil community are exposed to Bt toxins. Corn residue and macro-organisms were collected in Bt fields eight to ten months after harvest and analyzed for the presence of Bt toxin using ELISA. We found that Bt toxins remain in corn stalks and husks until at least ten months after harvest. The toxin was also detectable in residue-feeding soil organisms such as earthworms and isopods. This exposure study represents a first step for risk assessment studies to the impact of Bt corn on soil organisms.