Crystallization can be brought about in weakly vulcanized rubber by the method described by Thiessen and Kirsch for natural rubber. When samples of this type of vulcanized rubber were exposed to x-rays below + 6° C, but not under pressure, then Debye-Scherrer diagrams corresponding to those of a crystallized latex film were obtained. To determine the influence of pressure on these vulcanizates, samples were subjected to pressure on all sides in the chambers of the pressure apparatus described in the earlier work. After having been exposed for 100 days the sample which had been kept at + 6° C under 30 atmospheres' pressure showed a very marked Debye-Scherrer diagram, whereas samples kept at the same temperature but at normal pressure showed only the halo of an amorphous substance. Consequently pressure has an influence on the crystallization of vulcanized rubber as well as of raw rubber. The melting point of the crystalline phase lies between + 11° C. and +13° C. Obviously then an increase in pressure raises the temperature range of supercooling.