The steam reforming of dimethyl ether (DME) was performed on Cu/GaxAl10-xO15 and GaxAl10-xO15 catalysts (where `x' varies from 0 to 10). The presence of Ga2O3 in Al2O3 significantly affects the catalytic performance with respect to the DME conversion and the H, yield. It was found that the activity increases with the Ga2O3 concentration for GaxAl10-xO15. The DME steam reforming activity on Cu/GaxAl10-xO15 showed an improvement in the stability and H-2 yield as the Ga2O3 concentration increased. A correlation between the XPS results and the DME steam reforming activity for Cu/Ga(x)A(10-x)O(15) reveals that the heterogeneity of the surface is important for achieving a high H-2 yield. The specific interaction between Ga2O3 and Cu plays a decisive role in the distribution of Cu, which makes Cu/GaxAl10-xO15 active and stable for the reaction. (c) 2005 Elsevier B.V. All rights reserved.