This paper describes a study regarding the effect of Ni addition to NixMg1-xO solid solutions on the catalytic performances of ethanol steam reforming for hydrogen production. Nickel nanoparticles supported on NixMg1-xO demonstrated higher conversion of ethanol and yields of hydrogen than the bare support. We correlated the improved performances of Ni-based catalysts with the reducibility of nickel species. The addition of Ni to the solid solution support produced more easily reducible surface nickel species. Higher content of bulk nickel species in the support could inhibit the surface nickel species from diffusing into the bulk, leading to more surface nickel species that is easily reducible to its active form. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.