Analysis is undertaken motivated by the question : "What are the likely features and cost of a facility producing ethanol from cellulosic biomass at a level of maturity comparable to a refinery?" This question is considered with respect to cost reductions arising from increased scale, lower-cost feedstock, and process improvements in pretreatment and biological conversion, but not other process steps. An "advanced technology" scenario is developed that represents our estimate of the most likely features of mature biomass ethanol technology. A "best-parameter" scenario, intended to be indicative of the potential for R&D-driven cost reductions, is also developed based on the best values for individual process parameters reported in the literature. Both scenarios involve large plants (2.7 million dry t feedstock/yr). Feedstock costs are taken to be $38.60/delivered dry t for the advanced scenario and $34.00/delivered dry t for the best-parameter scenario. Projected selling prices, including operating costs and capital recovery corresponding to a 14.2% return on investment, are 50 cent/gal (pure ethanol basis) for the advanced technology case and 34 cent/gal for the best-parameter case. These are markedly lower than the 118 cent/gal selling price projected for base-case technology, with the largest share of cost reductions due to improved conversion technology. Key conversion technology improvements include, in order of importance, consolidated bioprocessing, advanced pretreatment, elimination of seed reactors, and faster rates. First-law thermodynamic efficiencies based on the biomass high heating value and production of ethanol and electricity are 61.2% for the advanced case and 69.3% for the best-parameter case, as compared to 50.3% currently. Combining advanced ethanol production technology of the type presented here with advanced gas turbine-based power generation is a promising direction for future analysis and may offer still further cost reductions and efficiency increases.