Pretreatment is vital to realizing the high yields essential to economic success, and the only unit operation more expensive than pretreatment is no pretreatment.  Thus, a team of researchers experienced with hydrolysis and fractionation of cellulosic biomass organized a Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) in late 1999 and early 2000 to develop comparative data on the more promising pretreatment options.  The CAFI team includes leading researchers from Auburn University, Genencor International, Michigan State University, Purdue University, the National Renewable Energy Laboratory, Texas A&M University, the University of British Columbia, and the University of California at Riverside.  The CAFI mission is to 1) develop information and a fundamental understanding of biomass hydrolysis that will facilitate commercialization, 2) accelerate the development of next generation technologies that dramatically reduce the cost of sugars from cellulosic biomass, and 3) train future engineers, scientists, and managers.  Through initial support by the USDA beginning in 2000, the CAFI team applied leading pretreatments of ammonia expansion, aqueous ammonia recycle, controlled pH, dilute acid, flowthrough, and lime to a single source of corn stover to facilitate technology selection.  The CAFI was then funded by the Office of the Biomass Program of the Department of Energy with cost sharing by Natural Resources Canada starting in 2004 to develop more comprehensive pretreatment, enzymatic digestion, and fermentability data for corn stover and poplar wood with the same pretreatments plus sulfur dioxide steam explosion.  Several posters will be presented summarizing CAFI results and cost estimates.