Barley stripe rust, caused by Puccinia striiformis f. sp. hordei, was introduced into South America from Europe in 1986. It spread to the U.S. in 1991 and since that time has been found in all principal barley growing areas of the western U.S.. From 1991 through 1997, over 38,771 barley lines were evaluated for barley stripe rust in field screening trials located in Bolivia, Germany, Mexico and Colorado. Barley lines rated resistant were planted at all locations the following year. In 1998 1,334 barley lines were evaluated for reaction to P. striiformis f. sp. hordei in Toluca, Mexico and Colorado. In the 1998 trials, 1,060 of the 1,334 lines were selections identified as Cooperator Germplasm. These lines were entered by ARS (Aberdeen, Idaho), North Dakota State University, Oregon State University, Utah State University, University of California at Davis, Washington State University, Coors Brewing Company, Busch Agricultural Resources, Plant Breeders 1, and Western Plant Breeders. Results were recorded for entry into the GRIN system at USDA/ARS at Aberdeen, ID. The numerous identified sources of resistance are available to both public and private sector U.S. barley breeding programs. Several cooperator lines evaluated in the program are being released to growers. A new variety, Bancroft (P.I 605474) is being released, based in part, on information obtained in this program.