The western corn rootworm (Diabrotica virgifera virgifera) is an economically important pest of maize in North America. In 2003, the U. S. Environmental Protection Agency approved the commercial use of Monsanto’s Bt maize expressing the Cry3Bb1 protein, which is toxic to pest Diabrotica beetles. However, given the previous adaptability of Diabrotica beetles to control measures, evolution of resistance to the toxin is a concern. To understand how resistance might evolve to the Cry3Bb1 we created a genetically diverse population of non-diapausing D. v. virgifera. Genetic variation from four geographically distinct diapausing D. v. virgifera populations were introduced into a non-diapausing colony through assigned and random matings. From this genetically diverse population we created three experimental and two control lines. Neonate larvae from each experimental line were exposed to Bt maize seedlings in a Petri dish containing agar. The time of exposure to the Bt maize seedlings increased each generation for several generations. Our goal was to achieve 80% larval mortality for each generation of selection. Initial exposure time was 24 hours and increased in 12 hour increments for five generations, and then we exposed the larvae in 24 hour increments for another five generations. Control lines were treated identically to the experimental lines except for the Bt exposure. Beginning with the fourth generation and alternating every other generation, we reared larvae from each line entirely on Bt maize to indicate the degree of resistance. Understanding how resistance to a transgenic crop can evolve could help in insect resistant management guidelines.