This experiment was conducted to identify the superior corn hybrids for silage production and to determine the combining ability of their parental inbred lines. A 7-entry diallel cross was evaluated for grain and stover yields, and agronomic characters under 3 different seasons. Hybrids Hi34 x Tx601, Hi26 x Hi34, and Hi29 x Hi34 showed high total dry matter yields. In general, late maturing hybrids had higher grain and silage yields than early maturing hybrids. Leaf area index was correlated with grain and stover yields. Rust rating was negatively correlated with yields and all characters, indicating that rust (Puccinia sorghi) was one of the major factors affecting yields. Diallel analysis showed that inbred Hi34 which was late in maturity and resistant to rust was the best combiner for both grain and silage yields. General combining ability (GCA) and specific com-bining ability (SCA) effects for yields and other characters were significant, suggesting that both additive and non-additive gene effects are involved for those characters. Ratio of GCA/SCA mean squares showed that GCA effects were more important than SCA effects for yields and other characters. GCA x season and SCA x season interactions were significant for grain and stover yields, revealing that gene effects were not stable for those yields under dissimilar environments.