We report on a heterogeneous precipitation method to modify the surfaces of La0.67Ca0.33MnO3 (LCMO) grains with CuO. It is shown that such a modification causes transport and magnetoresistance (MR) properties of the composites largely different from that observed in pure LCMO granular system. Especially, a significant enhancement in MR is observed near the insulator-metal transition temperature (T-IM). The maximum MR reaches as high as similar to 88 and similar to 90% at a low magnetic field of 0.3 T for the modified samples of LCMO/xCuO with x = 4 and 15 mol%, respectively. Compared to pure LCMO, the CuO-modified samples have a substantial decrease in resistivity (rho) at the temperature regions apart T-IM. Furthermore, for the x = 4% sample, a considerable thermal hysteresis is observed at the same temperature region where abnormal MR effect appears. On the basis of magnetization measurement and structural analysis, a possible interpretation for the experimental observations is presented. (C) 2007 Published by Elsevier Ltd.