Commercial corn hybrids were tested to assess several field and greenhouse techniques of evaluating corn rootworm tolerance. Root-system size and secondary root ratings obtained in the field correlated well with percentage root lodging in the field. Rootsystem size ratings obtained in the greenhouse were highly correlated with those ratings obtained in the field. Greenhouse evaluations effective detected differences among hybrids for root-damage rating, a measure of antibiosis, but field evaluations did not. Hybrids did not differ significantly for the amount of yield reduction incurred from rootworm injury.