In a microwave plasma-catalytic system, methane decomposition was carried out with 2.45 GHz microwave plasma and then the high conversion and yield of hydrogen and carbon black were obtained efficiently. It was found that hydrogen and carbon black were produced at the mole ratio of 2:1, and carbon black of around 30 nm was produced, which is comparable to classical furnace black. In a study of catalyst effect, Pt-loaded catalysts showed higher activities than a Pd catalyst for the conversion of methane by plasma-catalytic process. The productivity of carbon black increased with platinum loading up to 3 wt.%. (C) 2004 Elsevier B.V. All rights reserved.