Hydrogen fuel cell vehicles (FCVs) appear to be a promising solution for the future of clean and efficient personal transportation. Issues of how to generate the hydrogen and then store it on-board to provide satisfactory driving range must still be resolved before they can compete with conventional vehicles. Alternatively, FCVs could obtain hydrogen from on-board reforming of gasoline or other fuels such as methanol or ethanol. On-board reformers convert fuel into a hydrogen-rich fuel stream through catalytic reactions in several stages. The high temperatures associated with fuel processing present an engineering challenge to warm up the reformer quickly and efficiently in a vehicle environment. Without a special warmup phase or vehicle hybridization, the reformer and fuel cell system must provide all power to move the vehicle, including ¼ power in 30 s, and ½ power in 3 min to satisfy the Federal Test Procedure (FTP) cycle demands. If the reformer cannot meet these performance demands, hybridization can be applied. Battery power and energy requirements for a hybrid reformed gasoline FCV were determined using ADVISOR™ for a range of reformer system warmup durations (10 to 120 s). Finally, the predicted fuel economy impacts attributable to “cold-start” for a range of potential reformer warmup times and fueling rates for a gasoline-reformed FCV on the FTP cycle are analyzed.