The Food Protein Research and Developments Center's Industrial Crops Extraction Pilot Plant, with a nameplate capacity of 1 ton/24 h, was used to evaluate effects of shrub type, preparation methods, different solvents, and operating parameters on rubber yield. Shrub sources which have been evaluated include baled whole plants from USD A in Weslaco, Texas, and from Texas A&M plantings in Pecos, Texas. The USDA types included native, California bulk, dryland, and improved varieties. The A&M plantings evaluated were varieties 11,605 and 12,229. All shrubs were processed as received; that is their leaves were not removed. Toluene, xylene, pentane, and blends of pentane/perchloroethylene as solvents, in combination with methyl alcohol as precipitant, were investigated at different extraction and precipitating temperatures. Approximately 600 pounds of guayule rubber have been prepared during a series of runs over a 3-year time period on an actual plant-operating basis of around 4 months. Rubber yields on a daily time basis increased by up to 500% in comparison with a batch process developed earlier at the center. This dramatic increase is attributed principally to replacing the batch-mixing/screw-pressing extraction step with a continuous extraction operation. New shrub preparation and extraction conditions were determined and found to be critically important for high rubber recovery efficiencies. An additional precipitation step, downstream from the primary desolventizing screen used for precipitation of rubber, also improved recovery rates. Rubber yields as high as 92% of the rubber contained in the shrub, based on Soxhlet analyses, have been achieved. Shrub type and/or harvest time, age, and storage conditions were found to affect rubber yield. Additional processing highlights are also outlined. Selected molecular weight analyses and physical test results are indicative of overall premium rubber quality. Weight molecular weights, M(w), up to as high as 1.25 million have been obtained. Tensile strengths above 4150 psi have also been obtained.