Two separate studies were conducted to determine the genetic diversity of Hordeum species in different water environments. In the first study, 90 genotypes from both cultivated ( Hordeum vulgare) and wild barley ( H. vulgar spontaneum) species and in the second study, 64 genotypes from 15 other wild species of barley were evaluated for yield and morphological traits at three water environments (non-stress, mild stress and severe stress) in the field. In both studies, the results showed high genetic variation among genotypes for different traits. In the first study, mild drought stress reduced the mean values of most traits. Days to heading, number of fertile spike, plant height and number of seeds per plant did not change significantly under mild drought stress condition. Under severe drought stress, the mean values of all traits were significantly reduced, except for number of fertile spike.The heritability of traits had a wide range in this study. The highest heritability was observed for days to heading and the lowest heritability was observed for biological yield. The highest significant correlation was observed between grain yield and number of grains per spike. Based on the biplot of principle component analysis (PCA) in the first study in term of non stress environment, genotypes 51, 77, 76 and 82 of the cultivated species, in term of mild stress genotypes 28, 22, 25, 35 and 50 of H. vulgare Spontaneum and in term of severe stress genotypes 9, 12 and 36 of H. vulgare Spontaneum had higher potential for grain yield. In the second study, the mean values for the number of fertile spike, number of grains per plant, grain yield and biological yield were greater in mild stress condition. This maybe because the wild genotypes are more adapted to dry environments. The mean values for the grain yield and grains per plant did not change in severe drought stress, indicating that wild genotypes are resistant to drought stress and the mean values of the number of fertile spike and biological yield were greater in this condition. The heritability of traits had a wide range in the second study as well. The highest heritability were observed for plant height and spike length and the lowest one was observed for biological yield. Significant correlation was observed between grain yield and number of hundred seed weight in the three moisture environments. Based on the biplot of the PCA in the non stress condition, genotypes 54, and 55 of H. cordobense , in medium stress genotypes 63 and 64 of of H. bulbosum and in severe stress genotypes 34 and 39 of H. marinum were superior for the component related to the potential for grain yield. In comparing the average grain yield of species H. vulgare . spontaneum , H. vulgare , H.murinum and H.marinum it was revealed that the grain yield of H. vulgare was greater than H. vulgare . spontaneum and the average grain yield of H. vulgare . spontaneum was greater than both H.murinum and H.marinum in all three moisture environments. Based on cluster analysis the wild barley H. vulgare . spontaneum was grouped with H. vulgare in a same cluster and the other wild barley species were grouped in other clusters.