Colossal magnetoresistive (CMR) La0.67Ca0.33MnO3 (LCMO) and La0.67Sr0.33MnO3 (LSMO) films have been grown by pulsed laser deposition technique on GaAs(001) substrates buffered with epitaxial MgO layer. X-ray diffraction revealed strong c-axis out-of-plane orientation and strong in-plane texture of CMR/MgO bilayers on GaAs single crystal. The maximum temperature coefficient of resistivity TCR = 9.0% K-1 at 223 K and 2.0% K-1 at 327 K. and the magnetoresistance Delta rho/rho similar to-7.95% kOe(-1) and -1.47% kOe(-1) have been achieved for LCMO/MgO/GaAs and LSMO/MgO/GaAs heteroepitaxial structures, respectively. Comparison with the test LCMO and LSMO films grown directly onto the bulk MgO(001) single cry tal demonstrates the identity of LSMO/MgO/GaAs and LSMO/MgO films properties whereas the LCMO films grown on MgO buffered GaAs show lower transition temperature T-c = 242 K compared to 253 K in LCMO/MgO. (c) 2005 Elsevier B.V. All rights reserved.