An equilibrium model for agglomeration based upon the mechanism of grain boundary grooving in polycrystalline thin films is suggested. It involves an energy balance between surface, interface, and grain boundary energies, and predicts parameters which will influence the onset of agglomeration. It has been determined that small grain size, low grain boundary energy, high film surface and interface energies, and growth of single crystal epitaxial layers should promote resistance to agglomeration. Polycrystalline TiSi2 thin films deposited on Si substrates have been observed using cross-section TEM. The micrographs provide evidence that, for these films, the grain boundary grooving mechanism is dominant and most of the modeling assumptions are valid.