The effect of geometry in steam reformation is experimentally investigated with relation to the reactor output parameters of fuel conversion and temperature profile. The experimental facility includes two methanol-steam reformers of similar volume, but of different aspect ratios. Data collected from these experiments demonstrate the effects of reactor geometry and show that a redefinition of space velocity is needed for proper scaling of reactors. Conclusions and recommendations calling for further research involving this redefinition are drawn from the presented results. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.