Recent commitment from automotive manufacturers to manufacture prototype fuel cell vehicles in the near future has highlighted the need for fuel processing systems ready for automotive integration. Epyx Corporation (a subsidiary of Arthur D. Little) has developed an integrated fuel processing system designed for automotive load-following conditions. The system, a product of numerous design iterations and basic development, integrates a fuel processing assembly (FPA), CO clean-up device (PrOX), anode tailgas combustor (TGC), and a full control system. System development is ongoing to produce a fuel processing system ready for integration into automotive prototypes by the end of 2000. While continued fuel processor development is critical in creating a successful fuel cell system, issues such as air management, water recovery, hybridization, heat rejection, and turndown are major factors in system design. Epyx is coupling fuel cell system integration and testing with extensive modeling efforts to address these issues. Recent subsystem performance and modeling work shows the potential for a reliable system achieving greater than 40% system efficiency. Initial prototypes may not immediately realize this efficiency potential, but should compare favorably to existing automotive systems. Meanwhile, a clear technology development path exists to achieve >40% system efficiency within automotive constraints.