Here we show a method to hydrolyze cellulose selectively to glucose and cellobiose. sugars that can be easily fermented. Selecting an ideal ionic liquid ([EMIM]Cl), optimizing the dissolution time/temperature (15 min, 408 K) and the reaction procedure (addition of water during the reaction time) led to a very high selectivity to glucose + cellobiose (99.6%). (C) 2011 Elsevier B.V. All rights reserved.