Major impediments to the wide-scale implementation of hydrogen/air fuel cell vehicles are the lack of hydrogen infrastructure and on-board hydrogen storage. One proposed source of hydrogen exists in the development of on-board methanol (and other hydrocarbon) fuel processors. Packaging limitations and fuel processor performance constraints on efficiency and transient response play key roles in vehicular applications. These constraints may be addressed by considering proper thermal integration between two major components of the fuel processor: the reformer and catalytic burner. The focus of this research is on the effects of the catalytic burner on reformer performance in a thermally well-integrated configuration. Specifically, the work has focused on the generation of a detailed numerical model incorporating kinetics and mass and heat transfer to accurately characterize the burner. Unlike a simple, thermodynamic model, the detailed model provides a level of complexity necessary to understand the impact of thermal integration on reformer transient response, reformate composition, and emissions.