This document summarizes a study on combining ability analysis and nature of gene action for grain yield in maize hybrids. Researchers evaluated 20 parental lines, 4 testers, and 80 hybrids using a line x tester mating design. Analysis of variance showed significant differences among treatments for all characters studied. Both general combining ability (GCA) and specific combining ability (SCA) were important. The dominance variance had a major effect on hybrid performance, indicating non-additive gene action is important. The crosses with the highest SCA effects for yield were L8 x T1, L9 x T4, L3 X T3, and L16 x T2. These crosses involved parents with high GCA effects and could