The influence of Yb on Ni(20 wt%)/gamma-Al2O3 catalysts (prepared via a sol-gel method) for use in the dry reforming of methane was investigated. It was found that the addition of low quantities of Yb (1-2 wt%) led to significant increases in catalytic activity and catalyst stability, and the production of H-2 and CO at a ratio close to unity (similar to 0.95). Higher levels of Yb doping (3-8 wt%) did not achieve similar increases in activity as those observed in the lower level doped catalysts. Based on characterisation studies conducted on the catalysts before and after testing it was found that the catalyst with a low level of Yb (2 wt%) had the smallest average Ni particle size, narrowest particle size distribution and highest ease of reducibility (based on Temperature Programmed Reduction analysis). Analysis of the catalysts after testing showed that the catalyst with 2 wt% Yb also experienced the lowest level of carbon deposition and contained a high degree of graphitised carbon. The results obtained indicate that doping of Ni-Al2O3 catalysts with a select amount of Yb can give rise to a catalyst with excellent properties for use in the dry reforming of methane and that Yb can have a significant role in controlling the size/mobility of Ni nanoparticles produced via reduction of NiO. (C) 2012 Elsevier B.V. All rights reserved.