Biohydrogen holds the promise for a substantial contribution to the future renewable energy demands. It seems particularly suitable for relatively small-scale, decentralized systems, integrated with agricultural and industrial activities or waste processing facilities. Biohydrogen is considered as an important key to a sustainable world power supply and is currently being seen as the versatile fuel of the future, with the potential to replace fossil fuels. It has the key prospective to become the ideal means among the range of renewable H-2 production technologies presently existing. This review attempts to delineate the prospects and potentials of biohydrogen as renewable energy resource. (C) 2007 International Association for Hydrogen Energy.