Adsorption of cellulases to cellulose is a critical step in the hydrolysis of cellulosic substrates. However, the importance of adsorption in determining the hydrolysis rate is unclear. The accessibility to cellulases and specific hydrolysis rates were measured for various substrates. No correlation was found between the amount of enzyme adsorbed and the initial hydrolysis rate for different substrates. Specific hydrolysis rates were found to differ among substrates. Furthermore, both accessibility to cellulases and the specific hydrolysis rate of substrates were found to be changed by chemical and physical pretreatment of the substrate.