The objective of this paper is to evaluate three alternative formulations for simulating the steady-state flow and chemistry in a honeycomb channel for conditions that are typical of the catalytic combustion of natural gas. In developing simulation capabilities, it is important to understand the physical and computational accuracy that a model can deliver and the computational resources required to do so. Direct comparison of the solutions, using three different model formulations, reveal the range of validity of the various approximations. Computation times range from hours for the Navier-Stokes formulation to seconds for the plug-flow models. (C) 2000 Elsevier Science B.V. All rights reserved.