The effects of temperature (25-40 degrees C), H2SO4 concentration (31-70% (w/v)) and the acid/substrate relationship (1-5 cm(3) of H2SO4 per g(-1) of cellulose) on the solubilization rate of microcrystalline cellulose and on the glucose production rate have been analysed. The solubilization process was by determining reducing groups present in solution. For acid/substrate relationships of more than 1 cm(3) g(-1) and H2SO4 concentrations of greater than 62% (w/v), the acid promoted the total solubilization of the cellulose in the form of chains with a low degree of polymerization within 4 h. The solubilization demonstrated zero-order kinetics in which the specific rate and time of total solubilization are a function of the variables in operation. Glucose was produced according to a mechanism of two consecutive first-order pseudo-homogeneous reactions. The values of the kinetic constants k(1) and k(2) have been correlated with temperature, the H2SO4 concentration and the acid/substrate relationship.