A half diallel cross among developed eight yellow maize inbred lines and made at Gemmeiza  Agricultural Research Station, Agricultural Research center (ARC), Egypt during 2007 growing season . Parents , F₁ crosses plus two checks ( SC 166 and SC 3084) were evaluated at Gemmeiza and Sids Agricultural Research Stations in 2008 growing season. Data were recorded on grain yield, resistance to late wilt ,days to 50% silking , plant height and ear height. Data were genetically analyzed according to the procedures developed by Griffing (1956) method-4 model-1.The obtained results indicated that, mean squares associated with locations were highly significant for all studied traits except resistance to late wilt . Also, mean squares due to genotypes and their partitions : crosses, parents and parents vs. crosses showed highly significant differences. General and specific combining ability mean squares and their interaction with locations were highly significant for all studied traits. Also, the ratio of GCA /SCA revealed that  additive and additive x additive type of gene action were more important in expression of all traits under two locations and their combined. Inbred lines Gm.701 and Gm.705 have significant GCA effects for grain yield and resistance to late wilt, while inbred line Gm.709 considered the best combiner for earliness and  plant height under combined data. The eight crosses Gm.701 x Gm.705 (10.65 %), Gm.701 x Gm.712 (8.40 %) , Gm.705  x  Gm.710 (8.40 %),  Gm.701 x Gm.709 ( 8.07 %) , Gm.701 x Gm. 710 (7.10 %), Gm.715 x Gm.718 (6.13%) , Gm.705 x Gm.706 (3.55%) and Gm.712 x Gm.715 (2.86 %) had significantly positive heterotic effects relative to the highest commercial hybrid S.C. 166 in the combined over locations. These crosses are considered as promising genotypes for grain yield and could be used in maize breeding program.