The object of the investigation was to synthesize higher molecular compounds from natural rubber and from synthetic rubber by means of a process involving exposure to silent electric discharges. With both natural rubber and synthetic rubber, it was found possible to bring about polymerization by this method and to obtain polymers of various molecular sizes, which could be separated into two principal types: (1) polymers which remained soluble in benzene, and (2) polymers with a highly developed network structure, which were insoluble in benzene and therefore could be separated from the soluble polymers. After purification and drying, the insoluble polymers were obtained as inelastic, nonplastic products, in the form of soft, crumbly flakes. On the contrary, the soluble polymers retained the plasticity and elasticity of the original rubber, and behaved like raw rubber in the technical sense as well. This latter fact was proved by preparing a few mixtures and vulcanizates from these polymers, and it is noteworthy that a vulcanizate prepared from polymerized Buna-85 more nearly resembled a corresponding vulcanizate from untreated natural rubber than it did a vulcanizate prepared from the original, untreated Buna-85. Of course more extensive development work would be necessary to obtain polymers with particularly desirable properties from a technical point of view, and to find out how to compound these new polymers, e. g., what types and percentages of fillers, accelerators, and percentages of sulfur to use. Only in this way can the technical importance of these products be judged, and can any uses to which they may be applied to advantage be determined. But whatever may be their importance, the increased molecular sizes of these polymers of natural rubber and of Buna-85 are accompanied by marked increases in softening temperature without sacrifice of their technically important advantages of plasticity, tackiness and solubility. To this extent a not unimportant goal from the technical point of view may be regarded as having already been attained.