By coupling a well-stirred microjet reactor with Vacuum Ultraviolet (VUV) photoionization and a time of flight mass spectrometer (TOF-MS), we have developed a useful technique for studying hydrocarbon combustion and pyrolysis kinetics. The reaction occurs in a microjet reactor which allows immediate free jet expansion into vacuum, preserving trace non-equilibrium reaction intermediate species. The detection of these products with minimal fragmentation using single photon VUV ionization allows the direct determination of reaction intermediate parent species, simplifying the identification of probable reaction pathways. Preliminary results show products from the pyrolysis of ethyl acetylene at tempera lures from 300-1600 K. for ms reaction times. These results illustrate the advantages of using VUV-ionization mass spectrometry for the simultaneous detection of a wide-spectrum of pyrolysis and combustion products, especially where complex mixtures of hydrocarbons at ppm levels are present