The subject of this study was to determine the amount and composition of the pyrolysis products formed by pyrolysis of so called “Pyrolysis Resin”, which is a waste material formed during the cracking of light hydrocarbons to propylene. In the first part of this paper the pyrolysis products obtained at temperatures from 500° to 1000° in a molten metal bath were determined by direct chromatography. The products of thermal degradation consisted mostly of aromatic hydrocarbons. Benzene, toluene, xylene, indene and 2-methylindene were present in the amounts of about 1–2 %. Substantially larger amounts of naphthalene (about 20–25 %) were found at degradation temperatures of 900–1000°. The total weight of the pyrolysis procedure was determined over the same temperature range. “Pyrolysis Resin” investigated here is a high molecular weight organic residue that is usually removed as an unidentified material after pyrolysis of light hydrocarbons to propylene.