Two-year pot experiments with three varieties of spring barley were carried out. Water stress (water deficit of soil up to 40% of field water-holding capacity) was employed in four basic growth stages of plants: tillering, shooting (stem extension stage), ear formation and milk maturity. Reactions of the plants to water stress were expressed by a decline in the grain yield of the studied varieties throughout the growing season. The greatest losses in production of spring barley grain due to the experienced water stress of the plants were found at the beginning of ear formation and milk maturity stages of the grain. The sensitivity of the plants to the stress caused by water deficit in the soil during the initial period of their vegetative growth was smaller. Varieties showed significantly different sensitivities to the experienced water stress, depending on the growth stage during which the plants suffered from the stress.