Considerable effort has been made over the years to systematically collect, preserve, and identify the germplasm resources of barley on a worldwide basis. One of the largest collections of barley germplasm has been assembled and maintained by the United States Department of Agriculture at Beltsville, Maryland. This collection, numbering approximately 20,000 entries, is available to scientists throughout the world and has been utilized extensively in the continuing improvement and protection of barley cultivars for California. Researchers at the University of California at Davis have not only utilized this collection in their breeding programs but have contributed substantially to the identification of important sources of germplasm for specific plant characteristics, primarily in the area of disease resistance.