Methane decomposition over Ni, Cu and W containing catalysts to form acetylene was examined under microwave treatment. Three types of catalyst have been developed and tested in order to obtain an electric discharge on the surface while irradiating with microwave and, therefore, to initiate the chemical reaction. The effects of catalyst conformation, reaction time and microwave parameters were investigated. Methane decomposition efficiency, yield of acetylene formation and the amount and modality of coke deposition inside the microwave reactor were measured. The cooling of the surface of the catalyst was found to increase the value of methane conversion and acetylene selectivity and also helped to maintain the catalyst activity during longer processing times. (C) 2002 Elsevier Science B.V. All rights reserved.