The search for sustainable methods to produce traortation fuels is driven by concerns associated with its supply and demand and its impact on climate change and greenhouse gas (GHG) emissions. Nodaway, ethanol is widely recognized as the most important renewable liquid biofuel which can be produced from variety of feedstocks such as sugary, starchy, and lignocellulosic materials. Lignocellulosic materials are the most abundant sources of biomass in the world and have a high potential to provide an inexpensive and renewable feedstock for production of bioethanol. However, the recalcitrant nature of lignocellulose limits its chemical and biological degradation, and thus hinders the hydrolysis process. Pretreatment is a key step to overcome the lignocelluloses recalcitrance and make them more susceptible for hydrolysis by cellulases. Among the different pretreatment methods, treatment with cellulosic solvents has been suggested as the most efficient methods for enhancement of the saccharification yield. Pretreatment with cellulose dissolution reagents can be generally applied at milder conditions than the thermal pretreatments. The current study aimed at pretreatment of lignocellulosic materials including agricultural residues (e.g., sweet sorghum bagasse), and forestry wastes (e.g., birch and aspen woods) using cellulosic solvents such as sodium hydroxide, phosphoric acid, N-Methylmorpholine N-oxide (NMMO), and ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc). Pretreatment of sweet sorghum bagasse with sodium hydroxide (12%) and phosphoric acid (85%) was carried out at 0 °C (3 h) and 50 °C (30 min), respectively. Hydrolysis of the bagasse at 45 °C for 72 h using commercial cellulase and ?-glucosidase enzymes showed that the pretreatment could enhance the saccharification yield from 65% to 92%. Subsequently, the ethanol production yield in fermentation of hydrolysates (32 °C, pH 5.5) was efficiently increased from 50% to more than 80%. Analyses of the substrate revealed that the pretreatment resulted in lower lignin content and cellulose crystallinity together with increased surface area. However, sodium hydroxide and phosphoric acid pretreatments were more favorable for agricultural residues than for forestry wastes. The birch wood, one of the most common industrial woods, was pretreated with NMMO solution (85%) at 120 °C for 3 h. The results showed that the total carbohydrate content of the wood was almost preserved for further hydrolysis and bioconversion while its crystallinity was significantly decreased after NMMO pretreatment. Conversely, the NMMO considerably increased the swelling capacity of the wood. The yield of glucose production from birch wood was only 10% after 96 h enzymatic hydrolysis while it was promoted to 76% and 96% after 24 and 96 h hydrolysis of the NMMO pretreated wood, respectively. Furthermore, the ethanol production yield was highly increased (about 9-fold) as a result of the pretreatment. Aspen wood, one of the most stable woods available in the market, was pretreated with ionic liquid [EMIM]OAc for improvement of ethanol production. Without pretreatment, no appreciable amount of glucose was produced from the wood even after 72 h hydrolysis, while the ionic liquid pretreatment significantly increased the glucose yield from 5.3% to 95%. Accordingly, the pretreatment succeeded in improving the fermentability of aspen wood up to 81%. Analyses of the substrate by Simons’ stain and WRV methods showed noticeable increases in dye adsorption capacity and adsorption ratio even after a short time pretreatment with ionic liquid which is attributed to the major improvements in total surface area, pore sizes, and substrate accessibility to cellulase. Keywords: Lignocellulosic materials, Solvent pretreatment, Ionic liquid, NMMO, Enzymatic hydr olysis, Bioethanol