Epitaxial ferromagnetic manganite films have been sputtered on bicrystal substrates. Their magnetoresistance was measured as a function of magnetic field and temperature. The grain boundary magnetoresistance at low temperature is separated from the intrinsic magnetoresistance near the Curie temperature. The grain boundary magnetoresistance peaks at about 100 Oe and saturates at about 2 kOe. For aLa0.8Sr0.2MnO3film with a grain boundary angle&thgr;=36.8°a field independent componentr0=4.1×10−6 &OHgr; cm2was separated from a field-dependent component which has its maximumrH=2.3×10−6 &OHgr; cm2forHof order the coercive field. ©1997 American Institute of Physics.