B.t. corn is becoming a increasingly popular management option for north American corn producers struggling with the rootworm complex of beetles (Diabrotica spp.) Research was conducted to quantify the effects of B.t. corn on the fecundity and fertility of western corn rootworm (WCR) (Diabrotica virgifera virgifera Laconte) emerging from these crops in the field. Using field-collected adults from both the B.t. area and the refuge we evaluated, the fecundity and fertility of these individuals under the variety of mating scenarios that could be found in the B.t./refuge environment of a production corn field. The implications of this work for insect resistance management will be discussed.