Taylor-Couette flow with superimposed axial flow is becoming increasingly accepted as a novel reactor type offering a wide range of mixing regimes within a single reactor vessel, depending on the operating conditions of the reactor. To exploit the potential of such a reactor fully, the mixing processes in the reactor have to be well understood. A variant of an established model to simulate flow in a Taylor-Couette reactor with axial flow is presented. The model, which is based on the description of the flow as a linked network of stirred tanks, attempts to develop a parameterisation of the mass exchange processes between Taylor vortices and the by-pass stream on a rational basis. Some numerical results are presented and compared with results from the literature. (C) 2003 Society of Chemical Industry.