The highly endothermic commercial methane steam reforming (MSR) reaction was studied experimentally in a single-pellet-string fixed bed reactor. The temperatures inside the active catalyst particles, the temperatures on the outer surfaces of selected pellets and the exit gas composition were measured. The MSR reaction showed strong effects on the temperature profile along the reactor, causing it to decrease initially. A computational fluid dynamics (CFD) model was used to predict temperature and species profiles under the experimental MSR reaction conditions. Comparison of CFD and experimental data showed very good qualitative as well as quantitative agreement for temperature inside catalyst particles at different inlet gas temperatures, and for the temperature drop from outside to inside the pellets due to the reaction heat sink. Trends in methane conversion were also well-represented by the CFD simulation. (C) 2012 Elsevier B.V. All rights reserved.