Ethyl bromide or iodide at 20 torr was irradiated by a TEA CO2 laser. The reaction products were identified by means of infrared spectrometry, gas chromatography and CW CO2 laser photoacoustic spectroscopy. It has been proved that comparable amount of ethy-lene and acetylene are main products. It is reasonable to conclude that acetylene was produced directly from C2H5X via the simultaneous elimination of HX and H2 by laser irradiation and not brought by the subsequent photolysis of ethylene by the same laser.