Gold supported catalysts on ceria-alumina, prepared by different methods have been studied in the WGS reaction. For the synthesis of the mixed ceria-alumina support two methods were applied-a new method of mechanochemical activation and well known ceria washcoating on alumina. Gold catalysts on ceria-alumina, prepared by mechanochemical activation show a high and stable WGS activity. A correlation between redox activity of the catalysts, estimated by TPR and the catalytic activity of the samples was observed. The introducing of alumina to ceria by mechanochemical activation causes formation of oxygen vacancies, located mainly on the catalyst surface. In the freshly prepared catalysts an optimum between a part of positively charged nano-gold particles, Ce3+ and oxygen vacancies should be the crucial factor for the good performance of WGS catalysts. In the course of redox reaction the active complex is being changed because of the electron transfer between gold and ceria through oxygen vacancies. A positive effect of alumina on the catalysts stability with respect to avoiding gold and ceria particles agglomeration was confirmed, as well. (C) 2007 Elsevier B.V. All rights reserved.