The authors report ferromagnetism at room temperature in Co doped CeO2-delta thin films grown by pulsed laser deposition on SrTiO3 and Si substrates. On SrTiO3 ceria is epitaxied and displays a high crystalline quality. On Si the films are textured with a dominant orientation. While the ferromagnetism is little affected by the amounts of structural defects, it depends sensitively on the oxygen pressure during growth and annealing. This indicates that oxygen vacancies could be involved in the magnetic coupling between Co ions. Furthermore, the epilayers grown on SrTiO3 display a large magnetic anisotropy with an out of plane easy axis. (c) 2007 American Institute of Physics.