Pretreatment is expensive and strongly affects the cost and performance of most of the other operations.  To support selection of suitable technologies by industry, the Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) developed first-of-a-kind comparative data for application of the promising pretreatment options of ammonia expansion, aqueous ammonia recycle, controlled pH, dilute acid, flowthrough, lime, and sulfur dioxide steam explosion to poplar wood.  Common sources of biomass and enzymes were employed, and identical approaches were used to measure compositions and close material balances.  Although prior research showed more uniform performance with corn stover, important differences were observed in sugar yields from poplar using just cellulase.  Application of more severe conditions generally improved the results for all of the pretreatments, and supplementation with xylanases was particularly effective in improving sugar release from the solids produced by many of them.  The solids were characterized to identify fundamental features that could possibly influence performance.  Differences were observed in the results when most of these pretreatments were applied to two different sources of poplar wood that had substantial differences in lignin content.  The fermentability of the pretreated hydrolyzates and solids with a recombinant yeast strain was also assessed, with some requiring more conditioning than others to realize good ethanol yields.  Finally, a minimum ethanol selling price was estimated for each pretreatment based on the performance data developed and was heavily influenced by yield.  Overall, these results demonstrate the importance of evaluating pretreatment when integrated into the entire process.