The hypothesis that larvae of the western corn rootworm (WCR) are competitively superior to those of the northern corn rootworm (NCR) was tested under greenhouse conditions. Potted corn seedlings were inoculated with various numbers of embryonated eggs of each species to determine if the WCR would affect the survivorship or the spatial distribution of the NCR. The WCR reduced the survivorship and affected the spatial distribution of the NCR within the root system, whereas the NCR did not affect the WCR.