A half diallel cross between 7 inbred lines of maize was evaluated under two different nitrogen rates for six quantitative characters. Nitrogen rates, genotypes, parents, hybrids and parents vs crosses mean squares were significant for all traits. Significant genotype x nitrogen rate mean squares were obtained for days to 50% maturity, No. of rows ear^-1 and shelling%. Significant interaction mean squares between hybrids x nitrogen rates were detected for days to 50% maturity, No. of rows ear^-1 and grain yield plant^-1. General and specific combing ability (GCA and SCA) mean squares were significant for all traits. GCA/SCA ratios revealed that the additive and additive x additive types of gene action were the most important expressions for days to 50% maturity, number of rows ear-1 and shelling% in both and nitrogen rates and combined analysis. Significant interaction mean squares between nitrogen rates and GCA and SCA were detected for most traits. The crosses P₁xP₂ and P₁xP₇ at the low nitrogen level, P₁xP₄, P₁xP₆, P₁xP₇ and P₂xP₅ hybrids at the normal nitrogen level and the hybrid P₁xP₇ in the across nitrogen levels, were out yielded the check hybrid (Pioneer 30K8).  Also, single cross P₁xP₇ did not differ significantly from the hybrid Hytech 2031 in low nitrogen rate and combined analysis for grain yield plant^-1. The parental inbred line No. 4 gave a good combiner for No. of rows ear^-1 and grain yield plant^-1 at both and across nitrogen rate. The most desirable inter and intra allelic interactions were presented by combinations: P₁xP₆, P₁xP₇,   P₂xP₆   and   P₅ xP₆ for 100-kernel weight, P₁xP₂, P₁xP₄, P₁xP₆, P₁xP₇, P₂xP₃, P₂xP₅, P₂xP₇ and P₄xP₇ for grain yield plant^-1 and P₁xP₄ andP₄xP₇ for shelling%. These crosses may be prime importance in breeding programs either towards hybrid maize production or synthetic varieties composed of hybrids which involved the good combiners for the traits in view.