The objective of this work was to study the genetic systems controlling quantitative traits of maize using a North Carolina Design II mating design among nine parental lines and their 20 F1's under normal and drought stress conditions. Highly significant differences existed among studied genotypes, revealing a large amount of variability among them under both conditions. The significant values of mean square for parents vs. crosses were observed, indicating the importance of heterotic values and non additive genetic variance in the inheritance of these traits under the two conditions. Some lines and their F1 crosses showed drought susceptibility index "S" values less than one revealing relative drought resistance. The results showed that the magnitudes of non-additive genetic variance (σ 2 D) were larger than those of additive ones (σ 2 A) for most studied traits, indicating that the non additive gene action was pronounced in the inheritance of these traits. Therefore, these promising crosses could be utilized in maize breeding program to improve these traits under favorable and drought stress. This finding could be emphasized by the estimate values of narrow sense heritability.