A diallel cross among six bread wheat genotypes (parents) namely; Sids 1, Giza 168, Sakha94, Gemmeiza 9, Line 5 and Line 42 was carried out in 2008/2009 season to studay some genetic parameters in F1 and F2 generations for grain yield and its components i.e. plant height, noumber of spikes/plant, noumber of kernels/spike, 100- kernal weight and grain yield/plant. Genotypes mean squares were significant for all studied characters. Mean squares for parents vs crosses as an indication for heterosis were significant for all studied characters in the F1 and F2. Inbreeding depression was dectected in F2 for grain yield in 13 crosses and rangead from 22.94 to 59.71 % . Similarly, inbreeding depression, for number of spikes/plant ranged from 13.41 to 39.21 in nine crosses from 21.31 to 59.33 for number of kernels/spike in ten crosses, and from 16.28 to 72.91% for kernel weight in 11 crosses. Both general and specific combining ability (GCA and SCA, respectively,), were significant for all studied characters in F1. These results indicate the importance of both additive and dominance genetic effects in the inheritance of most studied characters. However, the additive gene action (GCA) was of great importance in the performance of most studied characters. Moreover, Results indicated that the cultivar (Giza 168) was good combiner for all studied characters while (line 5) was best combiner for plant height, number of spikes/plant and kernel weight. Moreover, the crosses(P2 xP5) , (P4x P5) and (P3xP6) are considered promising for grain yield improvement as they showed high specific combining ability effects.