A novel technique based on intermittent microwave heating (IMH) is used to prepare highly dispersed Pt/C catalysts. It has been proved that more than 60% Pt on carbon can be prepared by one-step procedure. The average Pt clusters on carbon are less than 5 nm with very narrow size distribution. The catalysts prepared by the present method show better performance in low temperature fuel cells. (C) 2004 Elsevier Ltd. All rights reserved.