A VARIETY of polymers have been subjected to irradiation in the Harwell pile, and electrons from a Van de Graaff generator, the results being followed mainly by X-ray diffraction. The initial effect is to break down bonds, some ionic, the majority covalent. The radicals formed can react in a number of ways. In the presence of oxygen they can form low-molecular weight compounds and carboxyl end-groups; different end-groups and low-molecular weight compounds can be formed in the absence of oxygen; they can reform the original bonds; or they can recombine in other ways.