Methane conversion using gliding arc plasma has been studied. The process was conducted at atmospheric pressure. Four kinds of additive gases-helium, argon, nitrogen, and CO2-were used to investigate their effects on methane conversion, as well as product selectivity, and discharged power. Methane conversion was increased with the increasing concentration of helium, argon, and nitrogen in the feed gas but decreased when CO2 concentration increased. Qualitatively, hydrogen and acetylene were the major gas products. No liquid product was produced. (c) 2005 Elsevier Ltd. All rights reserved.