La0.8Ca0.2MnO3 epitaxial thin films were fabricated on SrTiO3 (100) substrates by using pulsed-laser deposition (PLD) technique. The transport behavior upon treatments by applying a large dc current has been investigated. It is found that when the applied dc current exceeds a threshold value the electric resistivity in these films could be significantly enhanced in the whole measured temperature range from 10 to 300 K. Simultaneously, abnormal electroresistance behavior appears. The enhanced resistance turns out to be sensitive to a weak current. Even a very small dc current could remarkably depress the high resistance, showing an unusual colossal ER effect. ER reaches similar to 1175% at temperatures lower than similar to 50 K, and similar to 705% at 300 K for a current changing from 0.7 to 11 mu A. Structure measurements on micro-area by micron-XRD technique were carried out. No change of the structure and lattice parameter was found upon current treatments. (c) 2005 Elsevier B.V. All rights reserved.