Fuel processors for on-board hydrogen production have to meet numerous technical demands. They should be efficient, compact and lightweight, capable of different loads and able to perform cold start ups. In this paper, the recirculation of reformate is proposed as a means of efficiency enhancement. Different system configurations based on this idea are introduced and simulated. The resulting effect on the system's efficiency, the water balance as well as the impact of recirculation on the system's volume and weight are discussed. (c) 2006 Published by Elsevier B.V.