Ahalf diallel crosses among five durum wheat genotypes were investigated for plant height, grain yield and its components. The study showed equal importance of both GCA and SCA for all characters, except plant height and kernel weight. Plant height showed more importance for SCA (dominance gene action) as kernel weight was mainly under the control of additive type (higher GCA). Sohag 3 was the best combiner for grain yield/plant and its components number of spikes /plant and kernel weight, being followed by Banisewef I due to good general effects of number of kernels /spike and kernel weight The third one was Banisewef 3. Four crosses showed the highest mean performance and SCA effects and heterosis in grain yield /plant and at least one or two of yield components . These crosses were(PixP4), (P3xPs), (p < sub>3xp < sub>4) and (P2XP3) with heterosis estimates of 89, 26, 1 6 and 8 ⁰/0, respectively. Heterosis in grain yield and its components were related mainly to over dominance.Plant height, generally, showed positive over dominance toward tallness. Grain yield / plant and its components showed different types of dominance, being in different directions and averaging negative partial dominance for number of spikes/plant and number of kernels/spike, being positive fon kernel weight, while grain yield/plant averaged overdominance for increased yield.