Small structural differences in a series of closely related polymers may have a profound effect on the nature of their degradation reactions; neither may it be assumed that the degradation behavior of copolymers may be inferred from the behaviors of the homopolymers of the constituent monomers. Even the experimental conditions, the physical state of the polymer and the presence of impurities may have a profound effect upon the course of the degradation process. These generalizations are illustrated by reference to polymethacrylates and polyacrylates, methyl and phenyl substituted polysiloxanes and polyurethanes. -- AATA