Fabrication of superconducting MgB2 thin film on SrTiO3 and sapphire substrates by rf magnetron sputtering has been studied. We have tried both single target sputtering method using an Mg-excessive MgB2 target and co-sputtering of Mg and B. Argon sputtering pressure was 20 mTorr and 5% of hydrogen gas was added to trap the remanant oxygen gas in the deposition chamber. Films made by co-sputtering at room temperature followed by in situ annealing at 600 degreesC showed transition temperatures of about 24 K. However, those by single target sputtering or in situ co-sputtering showed either no superconducting transition or low T-c. (C) 2003 Elsevier Science B.V. All rights reserved.