Abstract: Environmental stress especially drought stress can play an important role in the reduction of plant growth and development. In order to study the effects of drought stress on different growth stages of wheat, an experiment was conducted with five Iranian variety included Atrak, Red-Seed, Cross-Flat, Hirmand and Darab. A split plot design was used with drought treatment being the main plot and cultivar the subplot with three replications. Poorest yield were when drought stress was applied at flowering. It was shown that the most sensitive crop stage in terms of the total number of spikelets is at early stem elongation. Onset of the drought stress at flowering had the greatest damaging effect on seeds per spikelet. The most damaging to seed size was drought stresses applied at and just after flowering. Significant interactions occurred because Darab the highest yielding cultivar and Red-Seed the lowest yielding cultivar both showed an equal and great reduction in seed size under the drought stress while Hirmand was much less responsive. Morphological characters are likely to be affected by water stress. The results of this study indicate that if water for irrigation is scarce and needs to be conserve any saving should not be at the risk of causing drought stress around anthesis. Hirmand, while not the highest yielding cultivar is more stable over the range of moisture stresses applied and it could be considered as a parent to combine its stability with the higher yield potential of say, Darab.