Drought stress respresents the most limiting factor for agricultural productivity in arid and semiarid regions of the world. This study was performed to evaluate the drought tolerance of cultivated and wild species of barley using drought tolerance and susceptibility indices (TOL, MP, GMP, SSI and STI) and some physiological traits. Genetic materials of first study involved 90 cultivated ( Hordeum vulgare . vulgare L) and wild ( H. vulgare . spontaneum C. Koch) barley genotypes. The second study was performed using 64 genotypes belonged to 15 wild species of genus Hordeum. Three water environments (control, mild stress and intense stress) were used to evaluate morphological traits, yield and its components of genotypes according to a completely randomized block design with three replications in each environments. Analysis of variance in the first study showed high variation between cultivated and wild barley genotypes for grain yield and drought and susceptibility indices. The highest and the lowest grain yield was observed in control and intense stress condition, respectively. The yield reduction caused by drought stress in cultivated genotypes were more than wild barley genotypes. Genotypes 64 and 78 from cultivated sub-species had the highest yield in control and mild stress conditions, respectively. Genotype 14 from H. spontaneum sub-species had the highest yield in intense stress condition. Results of second study showed considerable variation among genotypes of wild barley species. In this study, grain yield of all genotypes increased in mild and intense stress conditions than control. Genotypes 29, 39 from H. maranium and genotype 4 from H. murinum had the highest yield, in control, mild and intense stress conditions, respectively. Results of correlation analysis between mesured indices in both studies showed that three indices of MP, GMP and STI had high positive correlation with grain yield in normal and drought stress conditions and identified as the best indices. Based on these three indices, in the first study under mild drought stress condition, genotype 78 and under intense drought stress genotype 82 of cultivated suecies were identified as suitable genotypes. In the second study, based on the same indeices in both stress levels genotype 4 of H. murinum were found as the most tolerant genotypes and genotypes 54 and 48 as the most sensitive ones mild and intense stress conditions, respectively. Results from biplot of principle components analysis (PCA), in the first study showed that genotypes 76, 79 and 78 in mild stress and genotypes 82, 55, 64, 76 in intense stress conditions categorized in group A (high performance in both stress and control conditions) with high performance and low sensitivity to drought stress. In the second study, in both drought stress levels genotypes 6 and 4 were identified as the best genotypes with high performance and low sensitivity to drought stress which while genotype 57 had low yield potential and sensitive to drought stress. Results obtained from cluster analysis was a confirmation of the results of biplot of PCA. Results of variance analysis for physiological traits in both studies showed, significant differences among genotypes. Genotype by environment interaction for most traits was significant, suggesting various genotypes responses to moistures. In the first study mean of some physiological traits including relative water content (RWC), chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (Tchl) and carotenoids was reduced in mild stress conditions than control and intense stress than mild stress condition. In the second studyChla, Chlb, Tchl, carotenoids and proline increased under drought stress conditions. In the first study in mild drought stress level, harvest index showed a positive correlation with Chla, Chlb, Tchl and carotenoids while spike length had negative correlation with these traits. In the second study, in intense drought stress level, days to heading was positively correlated with Chla, Chlb, Tchl. The associations of traits can be usful for further indirect selection programs.