A half diallel set of six bread wheat (Triticum aestivum , L.)genotypes, genetically diverse, were done in all possible combinations excluding reciprocals in 1998/1999. In 1999/2000 growing season, the F₁ crosses and the six parents were grown in a field experiment in the Sakha Experimental Farm, Agricultural Research Center .The experimental design of randomized complete blocks with four replications was used . Plant height, number of spikes per plant, number of kernels per spike, 100-kernel weight and grain yield per plant were studied. The F₁'s of 15 wheat crosses and their respective parents were statistically analyzed to detect information on the genetic effects governing the studied characters. The obtained results showed that positive heterosis were detected for the six, two, nine and eleven crosses in case of number of spikes per plant, number of kernels per spike, 100 kernel weight and grain yield/plant ,respectively .The mean squares of genotypes, parents and crosses were highly significant for all studied traits .    The variances associated with general combining ability reached the level of significant in case of number of spikes per plant, 100-kernel weight and grain yield per plant. The same level of significance was found in case of specific combining ability for all studied traits. General combining ability variance were about two times higher than the specific combining ability variance for 100-kernel weight, suggested a predominant role of additive type of gene action. The variance due to additive genetic effects (D) was significant only for 100-kernel weight. The relatively proportions of variance due to non-additive effect, was significant and greater in magnitude than the additive component (D). Overall dominance effect of heterozygous loci (h²) was significant only for number of kernels/spike, which indicates that the effect of dominance is due to heterozygousity. Additive genetic components (D) appeared to be the major portion of the genetic variation for 100-kernel weight, which confirmed by the higher magnitude of GCA than those of SCA values. Over-dominance was observed for all studied traits. The proportion of genes with positive and negative alleles in parents showed that positive and negative alleles were not equally distributed among the parents for plant height, number of spikes/plant, number of kernels/spike and 100-kernel weight. Dominant genes in the parents were found for plant height and number of spikes per plant, number of kernels/spike, 100-kernel weight and grain yield per plant. Low values for heritability were detected for all studied traits, indicating that most of the genetic variances are due to non-additive genetic effects.