Pyrolysis gas Chromatographic isothermal and temperature programed separation of volatile components of unvulcanized natural rubber and synthetic polyisoprene was made on P-E columns Q and U. Besides identifications, relative quantitative differences between pyrolysis degradations of natural rubber and synthetic polyisoprene in pyrolysis temperature range 550°–750° C were established. It was found that the method was not suitable for an analogous study of vulcanized samples.