A model of the biotic potential of western corn rootworm (WCR),Diabrotica virgifera virgiferaLeConte, adult populations was developed from data presented in the literature. Adult emergence, adult populations, and egg populations were measured in a total of five continuous cornfields in 1982 and 1983. The simulations made with the model suggested that the observed populations of WCR adults and eggs were far below their potential (one-third and one-fifth, respectively). With the use of the biotic-potential model, adult population sizes were simulated by using different mortality (including dispersal) regimes. The results of these simulations suggest that age structure may be important in determining the potential of WCR adult populations. A regime that allowed the earlier emerging adults to remain in the field for a longer period fit the observed adult and egg population data better.