Polycrystalline La0.7Sr0.3Mn1-xFexO3 thin films, with x=0–0.12, have been prepared on (001)-Si substrates using pulsed laser deposition. The films consist of fine grains with an average size of 60–80 nm. For those films, the metal–insulator transition temperature, Tp, is much lower than the Curie temperature, TC. The high field magnetoresistance, HFMR, is nearly temperature independent for x≪0.08, whereas the extrapolated low field magnetoresistance at zero field, LFMR*, decreases rapidly with increasing temperature. Moreover, Fe doping significantly decreases LFMR* and enhances HFMR at low temperatures. We propose that for the Fe-doped films, both the reduced spin polarization of conduction electrons and the increased spin-flip scattering are responsible for the decrease of LFMR*, while the weakened ferromagnetic spin interaction at the grain boundaries is responsible for the enhanced HFMR. © 2001 American Institute of Physics.