Lignocellulosics dissolution in ionic liquids (ILs) present a promising pretreatment  strategy  for the conversion of biomass to ethanol. This study aims at optimising an imidazolium -based IL pretreatment  process . Biomass (sugarcane bagasse) samples  were  partially or completely dissolved in ILs, then recovered and partially fractionated by the addition of  different  antisolvents.  The kinetic measurements and material balances of biomass dissolution experiments show that ,   at least under laboratory conditions ,   high recoveries  and reuse  of  the  ILs can be achieved , though the biomass loading and choice of antisolvent have a significant impact on IL recovery.   The rates and yields of enzymatic hydrolysis of the IL pretreated cellulosic fractions are compared to dilute acid pretreatment process. All cellulosic products recovered from IL dissolution have enhanced saccharification kinetics compared to dilute acid pretreatment.  For example, the cellulosic fraction from 1-butyl-3-methylimidazolium chloride (BmimCl) pretreatment with 15 FPU/g of  Accelerase (Genencor)  is  75% hydrolysed in 90 minutes and 100% hydrolysed  in  < 6 hours.  By comparison dilute acid pretreatment resulted in  only 20% hydrolysis in 90 minutes and  75% hydrolysis after 74 hours. Optimisation of the IL pretreatment was achieved by varying temperature, time, biomass moisture content and loading conditions.