Adhesion forces of spherical alumina particles on ceramic substrates were studied. Results of direct force measurements using an atomic force microscope (AFM) were compared with theoretical results of a new rod model and with molecular dynamic computer simulation. Spherical alumina particles were produced by a flame process. The particles were glued to cantilevers, and interaction forces were measured by the AFM. A significant reduction of adhesion forces due to adsorbed layers was observed. The interaction volumes were determined by AFM scanning using a soft cantilever. The measured interaction forces were compared with calculated forces using the Hamaker concept including an adsorbed surface layer and the determined interaction volume (rod model). It turned out that calculated adhesion forces, neglecting deformation, are smaller than measured ones. This problem can be overcome if deformation according to Hertz is included in the rod model. Even for such a hard material as alumina, deformation occurs in the contact zone, which was also observed in a molecular dynamic computer simulation.