Miniature and microscale fuel processors that incorporate novel catalysts and microtechnology-based designs are discussed. The novel catalyst allows for methanol reforming at high gas hourly space velocities of 50,000 hr-1 or higher while maintaining a carbon monoxide levels at 1% or less. The microtechnology-based designs extremely compact and lightweight devices. The miniature fuel processors, with a volume less than 25 cm3, a mass less than 200 grams, and thermal efficiencies of up to 83%, nominally provide 25 to 50 watts equivalent of hydrogen, which is ample for the portable power supplies described here. With reasonable assumptions on fuel cell efficiencies, anode gas and water management, parasitic power loss, the energy density was estimated at 1700 Whr/kg. These processors have been demonstrated with a CO cleanup method and a fuel cell stack. The microscale fuel processors, with a volume of less than 0.25 cm3 and a mass of less than 1 gram, are designed to provide up to 0.3 watt equivalent of power with efficiencies over 20%.