Magnetotransport properties of magnetite thin films deposited on gallium arsenide and sapphire substrates at growth temperatures between 473 and 673 K are presented. The films were grown by UV pulsed laser ablation in reactive atmospheres Of O-2 and Ar, at working pressure of 8 x 10(-2) Pa. Film stoichiometry was determined in the range from Fe2.95O4 to Fe2.97O4. Randomly oriented polycrystalline thin films were grown on GaAs(1 0 0) while for the Al2O3(0 0 0 1) substrates the films developed a (I 1 1) preferred orientation. Interfacial Fe3+ diffusion was found for both substrates affecting the magnetic behaviour. The temperature dependence of the resistance and magnetoresistance of the films were measured for fields up to 6 T. Negative magnetoresistance values of similar to 5% at room temperature and similar to 10% at 90 K were obtained for the as-deposited magnetite films either on GaAs(1 0 0) or Al2O3(0 0 0 1) (C) 2007 Elsevier B.V. All rights reserved.