A comparison study of autohydrolysis and acid-catalyzed autohydrolysis of wheat straw was performed to understand the impact of acid addition on overall sugar recovery. Autohydrolysis combined with refining is capable of achieving sugar recoveries in the mid 70s. If the addition of a small amount of acid is capable of increasing the sugar recovery even higher it may be economically attractive. Acetic, sulfuric, hydrochloric and sulfurous acids were selected for acid-catalyzed autohydrolysis pretreatments. Autohydrolysis with no acid at 190<SUP>o</SUP>C showed the highest total sugar in the prehydrolyzate. Enzymatic hydrolysis was performed for all the post-treated solids with and without refining at enzyme loadings of 4 and 10FPU/g for 96h. Acid-catalyzed autohydrolysis at 190<SUP>o</SUP>C with sulfurous acid showed the highest total sugar recovery of 81.2% at 4FPU/g enzyme charge compared with 64.3% at 190<SUP>o</SUP>C autohydrolysis without acid.