Technical Abstract: New production areas need to be identified for guayule in order to meet the expected world-wide shortage of natural rubber by 2020. One promising area is the Texas High Plains region. For guayule to be grown in this region, more cold tolerant lines need to be identified. The objective of our study was to evaluate the performance of new guayule germplasm under the environmental conditions of the Texas High Plains. Guayule seedlings were transplanted May 18, 2006 at the Texas AgriLife Research Station at Halfway. Four released lines, AZ-1, AZ-2. AZ-3, and AZ-4; a released USDA cultivar (11591); and three unreleased breeding lines, N9-3, N6-5, and N13-1 were evaluated. Guayule cold damage was estimated in June of 2007 and 2008 using the following index: (1) no damage, (2) slight – injury of terminals to 6 cm, (3) moderate – 2/3 of plant volume injured, (4) severe – all aerial portions killed but resprouting, and (5) complete – beyond recovery with no regrowth. Plant harvests were conducted in April 2008 and March 2009. Following the 2006/2007 winter the cold damage index ranged from 1.2 in 11591 to 3.8 in AZ-1. The minimum air temperature was -15oC. There was minimal cold damage during the 2007/2008 and 2008/2009 winters. Biomass of the 24 month-old shrubs harvested in 2008 varied from 9,639 kg/ha in 11591 to 13,393 kg/ha in AZ-4. Shrub biomass in 2009 ranged from 26,721 kg/ha in 11591 to 32,951 kg/ha in N6-5. Rubber yield in 2008 was 222 and 639 kg/ha in AZ-3 and N6-5, respectively. Line AZ-3 yielded 717 kg/ha of rubber in 2009 while line AZ-4 yielded 2,006 kg/ha. Lines 11591 and N6-5 had the least cold damage and hold promise for establishment and rubber production on the Texas High Plains. Certain production criteria make the Texas High Plains an ideal guayule production site: the long-term annual rainfall averages 460 mm, irrigation water salinity is less than 1 E.C. and is pumped from only 909 m, and center pivots are available for establishing guayule by direct-seeding.