Extensive water-gas shift (WGS) reaction experiments have been conducted under different operating conditions to understand WGS process better. WGS kinetic rates were extracted from the experimental results and applied in a two-dimensional (2-D) unsteady kinetic model for performance and behaviour prediction. The model showed good agreement with the experimental data; a maximum error of 0.56% for hydrogen (wet basis) and 0.47% for carbon monoxide (wet basis) was observed for the H2O/CO ratio range of 1-7. Parametric studies on WGS reaction were also covered in this paper. By converting all the results of the parametric studies with respect to space velocity, the optimum range of WGS performance was determined. Our analysis showed that WGS process should be operated from 106.09 to 212.18/h and between 873 and 973 K. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.