The European corn borer [Ostrinia nubilalis (Hübner)] is an important pest of field corn (Zea mays L.) in the northeastern USA. One option for reducing yield loss from European corn borer (ECB) is the use of transgenic corn hybrids containing a modified Bacillus thuringensis (Bt) gene. This study evaluated Bt hybrids, their near isolines, and leading non-Bt hybrids for grain yield, moisture, and test weight under natural infestations of ECB in 2000, 2001, and 2002 at four to six locations across Pennsylvania and Maryland each year. Averaged over all locations and years, Bt, isoline, and lead hybrids yielded 9.1, 8.6, and 8.5 Mg ha−1, respectively. Grain moisture content at harvest was 224, 216, and 214 g kg−1 and test weight was 705, 713, and 713 kg m−3 for Bt, isoline, and lead hybrids, respectively. Overall, Bt hybrids produced higher yields, but also had higher grain moisture content at harvest and lower test weight than isoline and lead hybrids. Yield and moisture content differences were correlated with ECB infestations, but test weight was not. Isoline and lead hybrid yields were reduced by 2.37 and 2.60% respectively, for each ECB tunnel. Precipitation had no consistent effect on Bt and non-Bt hybrid differences for yield, moisture, or test weight. Delayed planting dates were associated with higher ECB infestations. This may be beneficial in predicting sites that could benefit from Bt hybrids. In some environments in Pennsylvania and Maryland, Bt hybrids can result in significant yield advantages.