Аннотация:The activating role played by ozone in enzymatic hydrolysis of aspen sawdust to sugars was studied. The effect of various parameters on effectiveness of ozonation (pH, moisture contents); changes in the structural characteristics of the samples by ozonolysis (specific surface area, cellulose crystallinity index); the relationship between the degree of delignification and the reactivity of wood in the process of enzymatic hydrolysis to sugars was investigated. As found, preozonation increases the initial rate and maximum level of hydrolisis, so that degree of conversion of wood to sugars rises by a factor of 10.