Understanding the inherent characteristics of wheat root related to development and drought resistance leading to successful production of dryland wheat yield are very important under conditions of Iran with large seasonal and annual variation in precipitation. The purpose of this study was to evaluate root growth and developmental characteristics and grain yield of dryland wheat cultivars under various environmental conditions. The experiment was conducted using factorial layout within a randomized complete block design with four replications in 2007 at the Isfahan University of Technology, Isfahan , Iran . The treatments were two irrigation regimes (irrigation after 50 and 80 percent depletion of root zone soil available water (SAW), two types of soil (namely Shervedan and Lavark) and four dryland wheat cultivars (Zagros, Koohdasht, Alborz and Falaat). The results showed that irrigation regimes, soil types, cultivars and their interactions significantly affected the root total dry weight (RTDW), depth, volume, surface and cumulative length. Irrigation after 80% versus 50% percent SAW depletion decreased the RTDW by 12 percent. Plants in Shervedan soil produced higher RTDW (26 percent) as compared to Lavark soil. Among the cultivars, Alborz and Falaat produced the highest and lowest RTDW, respectively. Falaat produced the highest and lowest RTDW in 50% and 80% SAW depletion regimes, respectively. RTDW of Alborz, Zagros and Falaat were lower by 0.243 gr (26 %), 0.307 gr (38 %) and 0.388 gr (49 %) in Shervedan versus Lavark soil, respectively. Conversely, RTDW of Koohdasht was higher by 0.142 gr (18 %) in Shervedan versus Lavark soil. RTDW of Koohdasht in Lavark soil was significantly increased with 80% SAW depletion treatment than others. Biological yield, above ground dry matter weight, grain yield per plant and harvest index were significantly affected (P?0.01) by irrigation regime, soil type, cultivar and their interactions. Grain yield decreased by 24 percent in 80% SAW depletion as compared to 50% SAW depletion regime. Plants in Shervedan soil had higher grain yield (24 %) than in Lavark soil. Koohdasht and Zagros had the highest and lowest grain yield, respectively. Among the root morphological characteristics studied, the cumulative root length (R = 0.48**) and root number (R = 0.46**) had the highest correlation coefficients with the grain yield. Among the cultivars studied, Koohdasht showed the highest yield potential under various environmental conditions and had the highest root development in deep soil. Thus Koohdasht might be suitable for further and detailed studies.