ABE fermentation had been a successful industry. In 1960s, this process was ceased due to increasing price of substrate (corn and molasses) as well as production of low cost petrochemical butanol. Considering the raw material cost as the main influencing expenses in the viability of the ABE industry, efficient use of low cost lignocellulosic materials as the carbon source has been suggested for production of biobutanol as an advanced biofuel. Cellulose composed more than 45% of the lignocelluloses, and its fraction increased to more than 70% through the pretreatments. Therefore, the hydrolysis of cellulose to glucose was firstly studied. After pretreatment, glucose yields of 85 and 95% were obtained by enzymatic hydrolysis using 5 and 15 FPU enzyme per gram of substrate, respectively. In addition, the yield of dilute acid hydrolysis was improved to 43% by a pretreatment. Different processes were investigated for efficient conversion of rice straw as an agricultural residue, pine as a softwood, and elm as a hardwood into fermentable sugars. The hydrolysates were then fermented by Clostridium acetobutylicum . The clostridia have the ability to ferment hemicellulosic pentoses as well as hexoses. However, the inhibitors presented in the lignocellulosic hydrolysates, mainly originated from lignin, negatively affected the ABE fermentation. Therefore, separation of lignin, recovery of hemicellulosic sugars, and efficient pretreatment and hydrolysis of cellulose were aimed in this study. Three pretreatments of dilute acid, autohydrolysis, and organosolv as well as combinations of them and three hydrolysis of dilute acid, autohydrolysis, and enzymatic hydrolysis were utilied to produce fermentable sugars from lignocelluloses. The results showed that the organosolv pretreatment at 180 °C for 30 min, the enzymatic hydrolysis, and fermentation was the best process for ABE production from rice straw (124 g ABE per kg rice straw). Furthermore, 105 g ABE was produced from each kg of pine by the process containing autohydrolysis, enzymatic hydrolysis, and fermentation. Using autohydrolysis, organosolv pretreatment, enzymatic hydrolysis of pretreated solid in autohydrlysate, and fermentation, 137 g ABE was produced from each kg elm. Compositional, structural, and morphological changes of the materials were analyzed by standard methods, e.g., FTIR, SEM, and related to the improvements. Keywords: Acetone, Butanol, Ethanol, Rice straw, Pine, Elm, Clostridium acetobutylicum .