Precision Combustion, Inc. (PCI) has developed and demonstrated an ultra compact and lightweight 2 – 5 kWe diesel and JP-8 reformer for fuels containing up to 100 ppm sulfur. The fuel processor includes the steam generator, fuel/air/water pumps, premixer, atomizer, igniter, sulfur cleanup (to <1 ppm) and a controller to enable stand-alone operation. The auto thermal reforming (ATR) reactor is based on a small, modular catalytic reactor, which utilizes patented Microlith substrates and catalyst technology. It has also been adapted for use with other gaseous and liquid fuels. The primary characteristic of PCI's ATR is that it operates on very low water flows (S:C  1) without coking and the reforming catalyst is sulfur tolerant. This permits meeting water needs via recycling from the stack exhaust as well as the long-term use of a ZnO desulfurizer. The reforming efficiency is >70% and its performance has been tested over hundreds of hours. The packaged fuel processor can be adapted for use with SOFC or PEM stacks. It has also been scaled up for 150 kWth operation. Its simple design permits meeting rigorous cost targets for economic viability.