This paper describes the effects of sodium chloride on H. vulgare during the whole of plant development. Rapid increases in sodium and chloride concentrations occurred during the early tillering, with little further change until grain formation. The net chloride and sodium intake did not change markedly during the major part of plant development, so that increases in sodium and chloride concentrations were prevented by the regulatory effect of rapid growth. During senescence the relative growth rate decreased and there were marked increases in chloride and sodium concentrations. Throughout the whole of plant development distribution of chloride, sodium, and potassium between plant organs were similar to those found previously during the early tillering stage, i.e. chloride and sodium concentrations increased and potassium concentrations decreased with age. Concentrations of sodium, potassium, and chloride in the grain were much lower than those in the rest of the plant. Treatment with sodium chloride changed the ion balance of the grain to a certain extent, but compared with the vegetative organs these changes in ion composition were very small. Potassium retranslocation was not impaired by high concentrations of sodium and chloride in vegetative organs. In a separate experiment, during the early tillering stage, sodium retranslocation was very slow and there was no sodium loss from the plant as a whole. Sodium, chloride, and potassium contents of the grain differed in the same order as retranslocation rates of these ions measured during early tillering. The data showed that ion regulation in the shoot was achieved both by growth of young organs and by selectivity during retranslocation. It is suggested that this selectivity occurs during uptake into, or transport by, the retranslocation system.