Non-catalytic microwave plasma technology was applied to the synthesis of acetylene from methane. Microwaves of 2.45 GHz were irradiated into a cylindrical quartz reactor connected to a vacuum line for successive supply of feed gas (pure methane). Acetylene was mainly produced with a selectivity of > 90%, accompanied by < 6% of ethane and ethylene when the output power level of the microwave was varied from 50 to 250 W. (C) 1997 Elsevier Science Ltd.