The performance of sulfite (SPORL), dilute acid (DA), and base (NaOH) pretreatments was compared in pretreating bamboo for enzymatic saccharification. The pretreatments were conducted in a microwave-accelerated reactor at 180 degrees C for 30 min with a liquor-to-bamboo ratio of 6.25:1 (v/w). Chemical loadings were 2% H2SO4 for DA pretreatment, 6 and 9% NaOH for base pretreatment, and 2-8% Na2SO3 with 2-4% H2SO4 for SPORL pretreatment (on oven-dry bamboo), respectively. Results indicated that unlike other grasses, bamboo was resistant to pretreatment due to high density and lignin content. The pretreated bamboo was hydrolyzed by 50-60% within 48 hours with an enzyme loading of 15 FPU cellulase and 30 IU beta-glucosidase per gram cellulose. The removal of hemicellulose seemed more critical to the enzymatic digestibility of a substrate than the removal of lignin when delignification was not extensive. In general, acidic pretreatments were more effective to bamboo than base pretreatments since the former removed more hemicelluloses than the latter. At similar content of lignin and hemicelluloses, SPORL substrate had better digestibility than DA substrate because the addition of small amount of sulfite made the lignin partially sulfonated, which reduced the hydrophobic impact of lignin on cellulases. Other advantages of SPORL pretreatment included high overall sugar yield, limited formation of fermentation inhibitors, and production of high-value lignosulfonate.