In this paper, we present an adaptive extremum seeking control scheme for a continuous stirred tank bioreactor with Haldane's kinetics. The proposed adaptive extremum seeking approach uses the kinetic model of the bioreactor to construct a seeking algorithm that drives the system states to the desired set-points that extremize the value of an objective function. Lyapunov's stability theorem is used in the design of the extremum seeking controller and the development of the parameter updating laws. Simulation experiments are given to show the effectiveness of the proposed approach. (C) 2003 Elsevier Ltd. All rights reserved.