Heritable resistance of corn (Zea maysL.) to feeding by the corn rootworm (Diabroticaspp.) complex has been reported, but little has been presented on the prospects of forming corn populations resistant to rootworm feeding. Tolerance, or the ability of lines to develop new roots in spite of rootworm infestation, was considered to be composed of 4 traits: decreased feeding damage; decreased root lodging; increased root size; increased secondary root development. The experimental material was composed of 221 random inbred lines developed from the Iowa Stiff Stalk Synthetic variety of maize. Root rating systems were utilized and selection was made for tolerance to corn rootworm damage. Estimates of heritability were calculated for each of the 4 root traits and indicated that selection on the basis of rootworm feeding damage alone would be ineffective. Heritability values for root sizes, secondary roots, and root lodging indicated that gains could be expected from selection for each of these traits. Genotypic, phenotypic, and error correlations were calculated and indicated that selection for larger root systems may result in superior secondary root development, reduced feeding damage, and reduced lodging.A retest of 50 superior entries indicated that selection for rootworm tolerance resulted in advance for each component trait of tolerance. The advance for each trait reinforces the existence of interrelationships among the 4 root traits. Superior lines selected from the retest population have been recombined into a single synthetic population, which should possess tolerance to corn rootworm feeding.