Acute and chronic toxicities were assessed in lab bioassays for over twelve species of adult Carabidae collected from a split-plot field experiment to determine effects of Bacillus thuringiensis (Bt) corn on coleopteran biodiversity in northeastern agroecosystems. Species selected were those dominant in pitfall sampling, and included members from the Agonum, Chlaenius, Harpalus, Poecilus, Pterostichus and Scarites genera. Toxicities for selected Cry3Bb1-containing corn tissues were compared to that of the targeted susceptible western corn rootworm, Diabrotica virgifera virgifera LeConte. Tissues from Bt corn and its near isoline were collected from the field for use in lab experiments on carabid beetles collected with pitfall traps from respective treatments. Immunoassays were conducted with a commercial ELISA kit for Cry3Bb1 to determine levels of this coleopteran-selective Bt toxin within expressed corn tissues and the resident soils. Understanding the impact of insecticidal transgenic corn and its residues on beneficial beetle species will aid in optimizing the commercial use of this biotechnology and addressing public perceptions.