Plant resistance offers a good alternative to pesticides for protecting corn (Zea mays L.) from attack by corn earworm, Helicoverpa zea (Boddie). The GT-CEW-RS8 synthetic is a breeding population with some resistance to corn earworm, but based on variability for this trait, further improvement was possible in this population. S₁ recurrent selection for corn earworm resistance was conducted to improve three synthetics derived from GT-CEW-RS8. The objective of this research was to study the effectiveness of these selection programs to increase insect resistance and maintain agronomic performance. Cycles of selection for each population were evaluated under four environments. Significant gains in resistance were realized, but all three synthetics derived from GT-CEW-RS8 showed a negative response for yield. However, yield losses were not very dramatic for 66RM4 and inbreeding depression would not affect the yield performance in hybrid combination. Selection for yield done simultaneously with selection for reducing ear damage by corn earworm and husk tightness could assist in avoiding decreased yield.