The growth and thermal stability of Cr clusters and films on single crystal SrTiO3 was characterized by reflection high-energy electron diffraction, X-ray photoelectron spectroscopy, scanning probe microscopy, and transmission electron microscopy. It could be shown that the Cr clusters nucleated with different epitaxial orientations depending on the deposition temperature. At temperatures above 700 degreesC, a chemical reaction was observed to occur between Cr and SrTiO3, which resulted in a change of epitaxy. Quantification of Ostwald ripening experiments allowed us to extract the activation energy of surface diffusion for Cr adatoms on SrTiO3 as E-d=0.44 eV.