The purpose of this work was to validate experimentally that multiple steady states may be achieved in a continuous stirred tank reactor (CSTR) during hydrolysis of sucrose by invertase. Experiments were done with four initial sucrose concentrations (0.1, 0.175, 0.584 and 1 M) to study their effect on residual sucrose and reaction rate at steady state. Two different steady states (S = 0.7 M, r = 9 x 10(-4) mol/l min and S = 0.135 M, r = 1.54 x 10(-3) mol/l min) were found depending on initial concentration of sucrose in the reactor. Two stable steady states were possible in a CSTR using invertase for the hydrolysis of sucrose. A third possible steady state can be derived theoretically, but it should be a metastable condition because any small disturbance in the system will result in transitory states stabilizing at sugar concentrations of either 0.135 or 0.7 M. (C) 2003 Elsevier Ltd. All rights reserved.