To determine the effect of drought in different phenologycal stages on yield and some of its components in four triticale varieties and one of wheat, drought was applied in six phenologycal stages 3 days before the occurrence of each phase to reach the permanent dry point. At this point plants remained 4 days. Then the usable humidity of the ground was about at 80%. A control was included. Significant differences were found in phenologycal stages, humidity levels, and genotypes in all evaluated characters. In terms of grain yield, the most susceptible stage was the boot stage with a 72% decrease, caused by decreases in the number of grains per plant (NG) and one thousand grains weight (TGW) of 52 and 44%, respectively. This effect can be attributed to the coincidence with the gametogenesis were the pollen formation was affected causing a 50% yield loss; probably, the pollen grain dehydration made difficult the fertilization, decreasing in 39% the NG. In the case of the apical differentiation the yield decrease was 52%, associated to losses of 27% in the number of ears and 33% in NG, caused by a collapse in the development of the ear. Drought during tillering caused a 41% decrease in the total dry weight, which explains a decrease in availability of photoasimilates for grain filling, reflected in the reduction of TGW (36%), which implied a 45% loss in grain yield. In the milky stage the decrease of yield (40%) was associated to losses in TGW (27%). The soft grain stage showed the smallest yield reduction (19%), caused by a possible decrease of the capacity of traslocation and a premature senescence. The boot, apical differentiation, and anthesis are the most susceptible stages to drought stress, where the number of grains per plant affects more intensively grain yield.