A reduced-order model is developed, allowing for a fast computation of the temperature field in multichannel microreactors. The model regards the fluid and the solid phase as interpenetrating continua and incorporates heat exchange between the two phases via a heat-transfer coefficient, characteristic for the channel geometry under study. The geometry of the channel walls determines the components of the thermal conductivity tensor, which govern conductive heat transfer to the envelope of the reactor. The mean-field model is solved numerically for a test case inspired from practical applications. Parallel to that, a detailed model based on standard methods of computational fluid dynamics is set up with the purpose to benchmark the results of the mean-field model. This full model incorporates the geometric details of the multichannel reactor and contains considerably more degrees of freedom than the mean-field model, resulting in a computational effort that is larger by at least a factor of several hundred. It is found that the temperature fields computed with the two models agree up to maximum deviations of about 3 K on a scale of 35 K. Thus, the mean-field model appears as an efficient tool to evaluate the thermal performance of multichannel microreactors, especially in the context of parameter studies or system optimization. (c) 2007 American Institute of Chemical Engineers.