Switchgrass has been highlighted as a leading herbaceous energy crop in the United States. As a part of a Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) Project among leaders in biomass pretreatment, our research is focused on optimizing total sugar yields from dilute sulfuric acid and sulfur dioxide pretreatment followed by enzymatic hydrolysis of the pretreated solids. Dilute sulfuric acid and SO2 were applied to switchgrass at concentrations from 0 to 5% over a temperature range of 140-220°C for times of 0 to 60 minutes, and sugar release from hemicellulose and cellulose were measured for pretreatment and the subsequent enzymatic hydrolysis of the resulting solids. Combinations of cellulases and hemicellulases were employed to identify combinations of pretreatment conditions and enzyme formulations that give the maximum total sugar recovery with the lowest possible enzyme loadings/cost. These results also provide a better understanding of switchgrass bioprocessing and new insights that will facilitate lower cost processes and commercialization of cellulosic ethanol technologies.