Dissolution of bagasse with 1-butyl-3-methylimidazolium chloride at high temperatures (110-160 degrees C) is investigated as a pretreatment process for saccharification and fermentation based biofuel production. Material balances are reported and used along with enzymatic saccharification data to identify optimum pretreatment conditions (150 degrees C for 90 min). At all pretreatment temperatures, dissolved and reprecipitated material is enriched in cellulose, has a low crystallinity and the cellulose component is easily and quantitatively hydrolysed (100%, 3 h, 15 FPU). At pretreatment temperatures, 150 degrees C, the undissolved material has only slightly lower crystallinity than the starting. At pretreatment temperatures 150 degrees C. the undissolved material has low crystallinity and when combined with the dissolved material has a saccharification rate and extent similar to completely dissolved material. Complete dissolution is not necessary to maximise saccharification efficiency at temperatures 150 degrees C. (C) 2011 Elsevier Ltd. All rights reserved.