Ensiling feedstocks is one proposed method for storing biomass for use in biorefineries.  Ensiling may reduce storage cost, minimize dry matter loss, inhibit feedstock combustion and increase feedstock processability.  While ensiling has been used to increase the digestibility of forage materials for livestock, the potential effect on feedstock processability has not been fully determined.  We compared the pretreatment and enzymatic hydrolysis performance of dried or ensiled corn stover with samples of the same material that had been dried or frozen immediately after harvest. These samples consisted of the frozen control material, plus dried and ensiled materials, with and without ensiling additives. Biomass was analyzed for feedstock composition and then pretreated using either dilute sulfuric acid or hot water. Liquors and solids were analyzed, and the solids were enzymatically hydrolyzed using a cellulase enzyme. We observed no significant differences in the combined yields resulting from pretreatment and enzymatic hydrolysis in xylose or glucose, between the frozen, dried or ensiled materials (0.05<p).  The acid pretreated materials exhibited higher yields across all categories compared to hot-water pretreated material. There were no significant differences (0.05<p) between ensiled samples that received ensiling additives, compared to those that didn’t receive ensiling additives. While ensiling did not appear to affect corn stover reactivity, we observed losses in structural sugar concentration in the ensiled materials.  Glucan losses averaged 11% from the initial glucan while xylan loss averaged 9%.  Further investigation is required to fully determine the effects and cost of ensiling on biomass storage and bioconversion.