Recent evaluations by the DOE and others indicate that large quantities of biomass grown in semi-humid and humid regions are likely to be harvested and stored wet rathert than in dry bales. Under anaerobic conditions wet storage frequently produces sufficient organic acids to limit biodegradation by reducing pH, resulting in significantly lower mass losses than in dry outdoor storage. Similar acid fermentations, commonly called ensilage, have been used for biomass storage in livestock production systems for over a millennium. This study investigates the interaction of ensiled storage with reduced severity dilute acid pretreatment, and examines the resulting impact on hydrolysis and saccharification. Results indicate ensiled storage creates a favorable environment for microbial and enzymatic biocatalysis, reducing required pretreatment severity, and subsequently increasing cellulose and hemicellulose hydrolysis to sugars for ethanol fermentation. Chemical and thermal pretreatment techniques currently constitute over 30% of the costs of biomass conversion to ethanol, so integration of beneficial wet storage strategies with pretreatment could significantly increase the economic viability of cellulosic biorefineries.