This study demonstrates for the first time that the enzymatic hydrolysis of cellulose is drastically enhanced following ultrasonic pretreatment of lignocellulosic material in ionic liquids (ILs) when compared to conventional thermal pretreatment. Five types of ILs, 1-buthyl-3-methylimidazolium chloride (BmimCl), 1-allyl-3-methylimidazolium chloride (AmimCl), 1-ethyl-3-methylimidazolium chloride (EmimCl), 1-ethyl-3-methylimidazolium diethyl phosphate (EmimDep), and 1-ethyl-3-methylimidazolium acetate (EmimOAc) were tested. Cellulose saccharification ratio was about 20% for kenaf powders pretreated in BmimCl, ArnimCl, EmimCl, and EmimDep by conventional heating at 110 degrees C for 120 min. Conversely, 60-95% of cellulose was hydrolyzed to glucose, subsequent to ultrasonic pretreatment in the same ILs for 120 min at 25 degrees C. The cellulose saccharification ratio of kenaf powder in EmimOAc was 86% after only 15 min of the ultrasonic pretreatment at 25 degrees C, compared to only 47% in that case of thermal pretreatment in the IL. (C) 2011 Published by Elsevier Ltd.