CYCLOPENTADIENE is the starting product for numerous syntheses. Thc presence in its molecule of a system of conjugated double bonds and a labile hydrogen atom of the methylene group explains the tendency of cyclopentadiene to polymerization, condensation, addition and organo-metaltic compound formation. From cyclopentadiene, synthesis resins, plastics, dyes, insecticides, drugs, plasticizers, anti-knock compounds and Ziegler type catalysts [1-9] can be obtained. However, the manufacture of these valuable products on a large scale is limited by the available supplies of cyclopentadiene which is, at present, mainly obtained from coal tar [10]. The raw material supplies can be increased substantially by using cyclopentadiene cantained in liquid distillates from high-temperature conversion of petroleum and petroleum derivatives to lower olefins. The extent of this process, as is well known, has rapidly increased in recent years in view of the demand for ethylene, propylene, dJvinyl and other lower olefins and dienes. It follows from the data of papers [11-13] and investigations carried out in our laboratory [14, 22, 23] that a substantial quantity of cyclopentadiene is contained in the liquid distillate from the cracking of petroleum derivatives; mainly low-octane gasolines and liquefied gases. Table 1 shows the results of studying the composition of hydrocarbon fractions C e from rapid contact cracking of various petroleum raw materials. Similar results were obtained by studying products of pyrolysis in tube heaters [24]. The figures given in Table 1 taking into account the rates of manufacturing olefins, indicate that the problem of satisfying the requirements of organic synthesis of cyclopentadiene can be solved quickly; the problem involves separation of cyclopentadiene from cracked distillates. It can be concluded from the patent literature [11-13] that cyclopentadienc can be readily separated from gasoline distillate and petroleum cracking by a method based on processes of dimerization, rectification, and sub-