In order to study the effects of terminal drought stress on morphological and physiological characteristics of 20 promising genotypes of barley, a split plot experiment based on randomized complete block design with three replications was conducted in the agricultural research center of Southern Khorasan during the 2007-2008 growing season. Treatments consisted of 2 levels of drought stress as main plots including the control (complete irrigation) and ceasing irrigation at 50% heading appearance, and 20 barley promising genotypes as sub plots. Results showed that ceasing irrigation at the 50% heading resulted in 14.64 and 8.12% reduction with the grain and biological yields compared to the control, respectively. Moreover, implementing drought stress from 50% heading onwards enhanced chlorophyll index, cell membrane permeability and declined the relative water content of the flag leaf. Although there were no significant differences amongst genotypes in terms of biological yield, the highest and lowest grain yields achieved with genotype numbers 18 (5997.2 kg.ha^-1) and 16 (3420.8 kg.ha^-1). The highest rate of chlorophyll index was recorded in genotype number 5 and 13, and the greatest amount of relative water content (80.7%) in the flag leaf was observed with the genotype number 8. According to the results of this study, genotypes number 18 and 20 provided the appropriate yield under both normal and drought stress conditions.