Monolithic three-way catalysts are applied to reduce the emission of combustion engines. The design of such a catalytic converter is a complex process involving the optimization of different physical and chemical parameters. Simple properties such as length, cell densities or metal coverage of the catalysts influence the catalytic performance of the converter.Numerical simulation is used as an effective tool for the investigation of the catalytic properties of a catalytic converter and for the prediction of the performance of the catalyst. To attain this goal, a two-dimensional flow field description is coupled with a detailed chemical reaction model.In this paper, results of the simulation of a monolithic single channel are shown. In a first step, the steady state flow distribution was calculated by a two dimensional simulation model. Subsequently, the reaction mechanism of the chemical species in the exhaust gas was added to the simulation process. The performance of the catalyst was simulated under lean, nearly stoichiometric and rich conditions. For these characteristic conditions, the oxidation of propen and CO and the reduction of NO on a typical Pt/Rh coated three-way catalyst were simulated as a function of temperature. The numerically predicted conversion data are compared with experimentally measured data. The simulation further reveals the coupling between chemical reactions and transport processes within the monolithic channel.