A comprehensive CFD-based modeling approach is applied to several automotive catalytic converters, with the objective of predicting thermal behavior under steady-state, high-load conditions. Specialized computational models are used to account for effects of heat and mass transfer in the monolith, oxidation reactions, heat generation, conjugate heat transfer in the various converter materials, and radiation heat transfer. These various physical considerations are assembled in a comprehensive CFD model, which is solved using state-of-the-art computational techniques. Detailed temperature measurements, taken in engine-cell experiments at Ohio State University's Center for Automotive Research, are used to validate the CFD models. Excellent agreement seen between measured and computed temperatures, both inside the converter assembly and on the outer shell. Trends in the predictions and experiments are discussed, with the aim of understanding the physical mechanisms of heat transfer in monolithic catalytic converters. An increased understanding of these heat transfer mechanisms can be used to improve converter durability at high temperatures.