A comparative study into the effects of total volume flow rate, methane 'residency time', methane volume flow rate, and steam-to-carbon ratio on the steam methane reforming process was performed in a model Direct Internal Reforming SOFC (DIR-SOFC) reformer operating in steady state at a nominal temperature of 973 K. The spatial distributions of major gas species (CH4, H2O, CO, CO2, and H-2) over the reformer surface were measured in-situ using Vibrational Raman Spectroscopy. Surface temperature measurements were recorded using IR thermometry. The effects of varying the intake mole fractions of methane and water were considered. The results of this work have demonstrated a strong positive correlation between the intake mole fraction of methane and the rate of the steam-methane reformation reaction. A weak negative correlation between the intake mole fraction of water and the rate of the reformation reaction was also shown. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.