The variables important to the development of pyrolysis gas chromatography as a means of identification of liquids and gases were studied by placing a pyrolysis tube at the inlet of a gas chromatographic column. The pyrolysis conditions can be controlled to limit the formation of methane and to yield the maximum quantities of other products for identification of the parent compounds. Conditions that reduce methane formation are the absence of air, low temperatures, a long residence time, and the use of quartz rather than stainless-steel pyrolysis tubes. There is a limited range of pyrolysis temperatures that permits the formation and observation of all products in a pyrogram.