In this paper, results of hydrogen production via methane reforming in the atmospheric pressure microwave plasma are presented. A waveguide-based nozzleless cylinder-type microwave plasma source (MPS) was used to convert methane into hydrogen. Important advantages of the presented waveguide-based nozzleless cylinder-type MPS are: stable operation in various gases (including air) at high flow rates, no need for a cooling system, and impedance matching. The plasma generation was stabilized by an additional swirled nitrogen flow (50 or 100 1 min(-1)). The methane flow rate was up to 175 1 min(-1). The absorbed microwave power could be changed from 3000 to 5000 W. The hydrogen production rate and the corresponding energy efficiency in the presented methane reforming by the waveguide-based nozzleless cylinder-type MPS were up to 255g[H-2]h(-1) and 85g[H-2] kWh(-1), respectively. These parameters are better than those typical of the conventional methods of hydrogen production (steam reforming of methane and water electrolysis). (C) 2007 Elsevier B.V. All rights reserved.