Efficient generation of hydrogen is an important enabling technology for commercialization of fuel cells for homes and cars of the future. A methodology for optimization of an autothermal reactor with respect to system parameters is described. Furthermore, a framework for theoretical interpretation of reforming reactions is developed using an atomic balance approach, which is utilized to determine the reforming reaction space and maximum monolith temperature for a methane reformer. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.