Superconducting MgB2 thin films have been prepared on MgO (111) substrates through a combined approach of chemical vapor deposition of boron and magnesium vapor diffusion. The resulting MgB2 thin films are pure-phase and polycrystalline. Both resistance and d.c. magnetization measurements of the MgB2 films show a superconducting transition temperature T-c of 38 K with a narrow width of approximately 0.1 K. Magnetic hysteresis measurements yield critical current density J(c) > 10(7) A/cm(2) at 10 K and 0 T. (C) 2003 Elsevier B.V, All rights reserved.