Using thermochemical calculations in the system Na-C-H-O, it is shown that when used in appropriate molar proportions carbon or methane, water and sodium hydroxide react to produce almost pure hydrogen and solid sodium carbonate. At 1 atm, the reaction takes place over a wide range of temperatures (100-800degreesC) producing hydrogen with only traces of other hydrocarbon impurities. Sodium carbonate is the byproduct of the reaction. (C) 2002 Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy.