The effect of crystal lattice disorder on the conductivity and colossal magnetoresistance in La 1−x Ca x MnO 3 (x ≈ 0.33) films has been examined. The lattice defects are introduced by irradiating the film with high-energy (≃ 6 MeV) electrons with a maximal fluence of about 2 × 10 17 cm −2 . This comparatively low dose of irradiation produces rather small radiation damage in the films.The number of displacements per atom (dpa) in the irradiated sample is about 10 −5 . Nevertheless, this results in an appreciable increase in the film resistiv-