Thin films of colossal magnetoresistance (MR) material, La0.67Ca0.33MnO3, were implanted with different doses (1011–1015ions/cm2) of 200 keV Ar+ions. The implanted samples were examined by ion channeling and x‐ray diffraction techniques. The channeling results clearly showed that the magnitude of the induced lattice disorder did not increase greatly for implantation doses up to 5×1013ions/cm2. In this low dose implantation regime, the magnetoresistance {MR=[R(0)−R(H)]/R(0)} increased by 50%, the peak resistivity went up by two orders of magnitude, and the magnetoresistivity peak temperature decreased by 130 K compared to the original, unimplanted sample. For doses ≥5×1013ions/cm2, the damage was significant and caused the sample to become semiconducting. ©1996 American Institute of Physics.