The kinetics of the sucrose decomposition in subcritical water was investigated using a flow-type reactor in the temperature range of 160-200°C and at a constant pressure of 10 MPa. The decrease in pH during the decomposition was linearly related to the logarithm of the conversion and significantly affected the decomposition rate. The sucrose decomposition was expressed by a kinetic equation of the autocatalytic type, where the decomposition rate of sucrose was proportional to the product of the concentrations of the remaining sucrose and acidic compounds, the most of which originated from the reacted sucrose. The equation was applicable to the sucrose decomposition at its feed concentrations from 5-250 g/l and at different pHs. The conversion of sucrose to glucose and fructose almost stoichiometrically proceeded in the stated temperature range. It was also indicated that the pH of the reaction mixture played an important role in the sucrose decomposition in subcritical water. © 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.