In CH4 dry reforming, the influence of Ca on the activity of supported Ni catalyst depended on the properties of the supports (SiO2, alpha-AlO3, gamma-Al2O3) and on the amount of Ca added. Small amounts of Ca increased the activity and stability of Ni/alpha-Al2O3. Temperature-programmed reduction with H-2 (H-TPR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterizations of Ca-promoted Ni/alpha-Al2O3 catalysts indicated that Ca improved the dispersion of Ni, strengthened the interaction between Ni and Al2O3, and retarded the sintering. A higher amount of Ca covered the surface of alpha-Al2O3 and enhanced the decomposition of CH4. (C) 2003 Elsevier B.V. All rights reserved.