When subjected to atomic energy radiation certain polymers crosslink, a process which is equivalent to vulcanization, but occurs without the admixture of extraneous chemical agents. Other polymers degrade by main chain fracture, a process which occurs at random throughout the molecule, and is different from thermal or ultraviolet degradation. Methods available for detecting crosslinking in irradiated polymers, include those based on solubility and swelling which have been used to study the effect of high energy radiation on a number of natural and synthetic rubbers. The polymers investigated include natural rubber, polychloroprene, polyisobutylene, polybutadiene, and thioplasts, as well as some copolymers. The results show the degree of crosslinking to be proportional to radiation dose, and to be reduced by the presence of styrene or acrylonitrile units in copolymers. Possible applications of this physical technique of linking molecules are discussed briefly.