Switchgrass has been highlighted as a leading herbaceous energy crop to support large scale production of biofuels in the United States.  As a part of phase III of a Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) Project among leaders in biomass pretreatment, our research focused on optimizing total sugar yields from switchgrass by batch pretreatment with dilute sulfuric acid or sulfur dioxide followed by enzymatic hydrolysis of the pretreated solids. In this work, dilute sulfuric acid and SO₂ were applied at concentrations ranging from 0 to 5% over a temperature range of 140-220°C for times up to 60 minutes, and glucose and xylose  yields were measured for the overall operations of pretreatment and subsequent enzymatic hydrolysis.  Different combinations of cellulases and hemicellulases were also applied to identify the best pretreatment conditions and enzyme formulations that give the maximum total sugar yield with the lowest possible enzyme mass and cost.  These results were directed toward understanding how dilute acid and SO₂ pretreatment impact total sugar yields from switchgrass and to gain new insights that facilitate identification of lower cost processes and facilitate commercialization of cellulosic ethanol technologies.