Pretreatment with N-methylmorpholine-N-oxide (NMMO), phosphoric acid, and sodium hydroxide was evaluated for improvement of dilute-acid hydrolysis of cotton fiber, the most difficult to break down cellulose. The pretreatments improved the yield of glucose formation by acid hydrolysis. Compared to the other methods, phosphoric acid pretreatment resulted in higher glucose yields and minimal byproduct formations by hydrolysis under milder conditions. Furthermore, the solid residue of the hydrolysis was subjected to enzymatic hydrolysis in order to convert the remaining cellulose to glucose. Different combinations of parameters in dilute-acid and enzymatic hydrolysis were considered for obtaining a high glucose yield with minimal enzyme loading. A process involving phosphoric acid pretreatment, dilute-acid hydrolysis, and enzymatic hydrolysis using only 5 FPU/g cellulase and 10 IU/g beta-glucosidase resulted in total glucose yield of 95.4%, and fermentation of the hydrolysates resulted in a yield of 458 g of ethanol/kg of initial cellulose (0.47 g ethanol/g glucose).