Greenhouse experiments were conducted in 2004–2006 to examine the reciprocal effects of aboveground herbivory by European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), and belowground herbivory by root-knot nematode, Meloidogyne incognita Chitwood (Tylenchida: Heteroderidae), on one another at three corn, Zea mays L., growth stages. Two experiments were conducted to study the effect of aboveground herbivory by O. nubilalis on the number of M. incognita juvenile penetration/root system and eggs/root system. In the first experiment, the O. nubilalis infestation level by plant growth stage main effect interaction was not significant for either M. incognita juvenile penetration or eggs. The overall effect of stalk tunneling by O. nubilalis resulted in 48.9% fewer juvenile penetration and 40.0% fewer eggs than in the respective controls. In the second experiment, the main effects interaction was significant for juvenile penetration (P = 0.0422) and eggs (P = 0.0134). At the eight- and 10-leaf growth stages, the combined effect of one and three O. nubilalis larvae per plant resulted in 41.2 and 44.7% significantly fewer juvenile penetration than in the respective controls. Similarly, the combined effect of stalk tunneling (with the exception of one larvae per plant at the 10-leaf growth stage) at the six-, eight-, and 10-leaf growth stages resulted in 46.3, 53.3, and 55.2% fewer eggs than in the respective controls. In all instances, M. incognita juvenile penetration and eggs were significantly negatively correlated with O. nubilalis tunnel length. In a reciprocal experiment conducted two times, no significant (P > 0.05) effect of M. incognita inoculation level on stalk tunneling was found in either experiment.