Combining ability and heterosis for grain yield and yield components traits, were studied in a six-parent diallel cross without reciprocals. The 15 F₁ hybrids and the six parental cultivars were grown at 2009/2010 season at the Experimental Farm of Faculty of Agriculture, Al-Azhar University, Assiut Branch. Seeds were planted in a randomized complete block design with three replications. The data showed that, the mean squares of the genotypes (six parents and 15 F₁ hybrids), GCA and SCA were highly significant for all studied traits except SCA for plant height which was insignificant. The effects of general combining ability (GCA) were highly significant for all the traits measured with the exception of 1000-grain weight trait, while the specific combining ability (SCA) effects were statistically significant for studies traits. The GCA effects clarified that, the parents P₁, P₃ and P₅ were the good general combiners for most studied traits. On the other hand, the estimates of SCA effects exhibited the highest SCA values regarding the cross P₃ × P₆ for days to 50% blooming, the cross P₃ × P₅ for plant height, the cross P₂×P₆ for number of spikes/plant, number of grains/ spikelet and grain yield/plant, the cross P₂×P₄ for number of spikelets/ spike and the cross P₅× P₆ for 1000-grains weight. The heterosis versus mid-parents and better-parent elicited highly significant or significant and positive or negative for days to 50% blooming, number of spikes/plant, number of spikelets/spike, 1000-grain weight, number of grains /spikelet and grain yield/plant. The best crosses for these traits in ranking were P₁ × P₂, P₃ × P₅, P₂ × P₆, P₂ × P₄, P₅ × P₆, P₂ × P₆ and P₂× P₆. Generally, it could be concluded that the best promising combinations were the previous crosses.