The concept of cogeneration of power and hydrogen plants is introduced with specific regard to the fossil fuels. Fossil fuels require steam to be converted to hydrogen, while powerplants usually discharge heat by condensing steam. Moreover, hydrogen can be burned with oxygen to produce steam and to generate power in high-temperature steam cycles. These considerations suggest that an integration of the processes could result in a very high efficiency of conversion. It could allow to start immediately to convert efficiently fossil fuels to power and clean hydrogen. Some theoretical evaluations are carried out which show that an improvement of efficiency could be reached with respect to separate plants. However, it is necessary to investigate each specific case in order to evaluate the real advantage obtained. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.