Maize (Zea mays L.) is the third most important cereal grain in Egypt (after wheat and rice) but it is vulnerable to water stress which causes lead losses in both yield and quality. In the current study we evaluated 100 S1-lines along with their top-crosses using two testers under normal and water stress conditions. We used line × tester to assess general (GCA) and specific (SCA) combining ability effects for 100-grain weight and grain yield per plot; In addition, we estimated heritability for both traits. Result of line × tester analysis showed highly significant differences among parents, crosses vs parents., In addition, between testers and lines × testers for both traits under normal and water stress condition. The results, lines showed non-significant for 100-grain weight under normal and water stress condition. Grain yield per plot showed non-significant differences under normal condition while it showed significant under water stress condition. Under normal condition, S1-lines 56 and 88 possessed the highest 100-grain weight while, the highest values of 100-grain weight were found in cross combinations including S1-line 29 × SC162 and S1-line 61× TWC352. On the other hand, S1-lines 65 and 68 possessed the highest grain yield per plot while, the highest values of grain yield per plot were found in cross combinations including S1-line 86 × SC162 and S1-line 37× TWC352. Under normal condition, S1-lines 10 and 99 displayed positive and significant GCA effects for 100-grain weight while, S1-line 86 and 55 exhibited the maximum GCA effect for grain yield per plot. Top-crosses including S1-line 29×SC162 and S1-line 75×TWC352 were good specific combiners for 100-grain weight while, the top-crosses including S1-line 29×SC162 and S1-line 78×TWC352 were good specific combiners for grain yield per plot. Heritability in broad sense showed moderate highly estimates for both traits. Our results indicated the preponderance of dominance gene action in controlling both aforementioned traits. In conclusion, these S1-lines are promising to produce drought tolerant inbred line in the future, which may lead to produce drought tolerant hybrid.