The simulation model originally described in Storer et al. 2003 is used to evaluate the role of pyramided Bt cotton and corn cultivars, EPA mandated non-Bt refuges, and soybean as a host in H. zea resistance development to Bt in eastern North Carolina. The model was refined by Livingston to include pyramided Bt cotton and corn cultivars, but H. zea survival on pyramided cultivars was based solely on theoretical data. To convincingly identify the most influential factors in resistance evolution, empirical estimates of H. zea survival on these cultivars were incorporated into the model. The model predicts that pyramided Bt cultivars and soybean as a host both greatly delay resistance development. With pyramided Bt cultivars, the model also predicts that the 20% sprayed non-Bt cotton refuge's contribution to delaying resistance evolution is greatly supplemented by other non-Bt sources of susceptible moths and has less of an effect on Bt resistance management than the non-Bt corn refuge in eastern North Carolina.