The processes for hydrogen production discussed in this paper are those for which water is the only material input and hydrogen and oxygen are the only material outputs: H2O + X --> XO + H-2 XO --> X + 1/20(2) [GRAPHICS] H2O --> H-2 + 1/20(2) Furthermore, the required energy inputs are meant to be mainly heat (rather than useful work, such as electricity). As shown above, these processes may be visualized as a set of chemical reactions which sum the decomposition of water. (C) 2001 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.