The thermolysis of nickel acetylacetonate supported on alpha-alumina has been investigated by thermal methods (TGA-DTG-DTA), infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). At 250 degrees C and in static air atmosphere, decomposition of the metal ligands is nearly complete. Higher temperatures are needed in an inert atmosphere or in a vacuum. The variation of XPS peak parameters of samples heated at various temperatures between 120 and 900 degrees C has been interpreted as a change of the distribution of the Ni species between the octahedral and tetrahedral aluminum sites of the support, and a progressive formation of a nickel aluminate-like species, in agreement with temperature-programmed reduction features.