This paper deals with the B-BAC (balance-based adaptive control) methodology and its application to the control of the non-isothermal CSTR. This new control methodology combines simplicity and generality, characteristic for the classical PI controller, with very good control performance and robustness resulting from its adaptability and feedforward action. The final form of the B-BA Controller is derived on the basis of the general first-order dynamical model in which all unknown non-linearities and modelling uncertainties are replaced by the only one time-varying parameter. The on-line estimation of its value allows for the adaptability of the controller. In this paper, it is also shown how to apply this B-BAC methodology to control the non-isothermal CSTR. The very practical case is considered as we assume a very large uncertainty on the complete model of the process and especially on its non-linearities. Thus, the simplified phenomenological model is derived only on the basis of the energy conservation law. The simulation results prove very good control performance of the B-BA Controller in comparison with the classical PI controller and in the presence of the disturbances changes and of the significant uncertainty on the measurement data. (c) 2005 Elsevier B.V. All rights reserved.