Technical Abstract: 'Sidney' (Reg. No. , PI 641939) is a spring, two-rowed, Russian wheat aphid-resistant, feed barley (Hordeum vulgare L.) developed for the high dry plains of eastern Colorado and western Nebraska where RWA is a persistent pest. Sidney was developed by USDA-ARS, in Stillwater, OK, and tested cooperatively by USDA-ARS, in Stillwater, OK, and in Aberdeen, ID, Colorado State University, and University of Nebraska. Russian wheat aphid (RWA) [Diuraphis noxia, (Kujomov)] resistance in Sidney was transferred from STARS 9301B into an Otis background by three backcrosses. Sidney is resistant to all known biotypes of RWA in the US. Grain yield of Sidney is superior to that of Otis in the presence of RWA and equal to Otis and Otis + Gaucho in the absence and of RWA. Barley production on the marginal crop lands of the high plains became economically and environmentally prohibitive with the introduction of RWA to the US. Sidney was developed to bring barley back into crop rotations which are important for moisture and soil conservation of these marginal production areas.