The growth of Co on Au/mica has been studies by means of variable temperature scanning tunnelling microscopy and Auger electron spectroscopy. Growth at 300 K (low Co coverage), produces mono- and bilayer islands of about 5 nm in diameter. Rough Co layers are obtained upon further deposition of Co. Direct growth at 430 K leads to much larger and higher Co islands. Their surface density is no longer dictated by the nucleation at the dislocation of the root-3 x 22 reconstruction of the Au(111) surface but rather by the growth kinetics of diffusing Co atoms. Annealing at 500 K of films grown at 300 K leads to significant surface smoothing possibly induced by migration of Au on top of the Co film.