A total of 211 sorghum, Sorghum bicolor (L), genotypes were evaluated (1981, 1982, and 1983) for resistance to leaf feeding by 1st-generation European corn borer (ECB), Ostrinia nubilalis Hubner, larvae under heavy infestation conditions (ca. 750 eggs/plant). All sorghum hybrids were resistant. Some sorghum hybrids were not as resistant, however, as a highly resistant inbred line of maize, Zea mays L;First-generation larval mortality was rapid on four sorghum hybrids (92.2 - 97.7% mortality within 6 days after egg hatch), but larval mortality was not as rapid on four sorghum hybrids as was larval mortality on a resistant maize inbred (99.1 - 99.7% mortality within 6 days after egg hatch). The majority of 22,827 1st-generation larvae fed on leaf tissue in the moist area deep in the whorl of sorghum and maize plants. Resistance in sorghum, as in maize, to 1st-generation ECBs, therefore, is resistance to leaf feeding (a high level of antibiosis against 1st- and 2nd-instar larvae). Dried-ground leaves (substituted for wheat germ in a meridic diet) of resistant genotypes of sorghum and maize had no deleterious effect on survival and development of ECB larvae compared with a diet containing leaves of susceptible maize and compared with a standard wheat germ diet;Second-generation larval mortality was rapid on four sorghum hybrids (93.9 - 98.9% mortality within 6 days after egg hatch) and on two resistant maize inbreds (92.6 - 97.8% mortality within 6 days after egg hatch). The majority of 33,690 2nd-generation larvae fed on sheath-collar tissue through 35 days after egg hatch of sorghum plants and through 15 days after egg hatch on maize plants. Resistance in sorghum to 2nd-generation ECBs as in maize, therefore, is resistance to sheath-collar feeding (a high degree of antibiosis against 1st- and 2nd-instar larvae).