The oxidative degradation of polymers is triggered by exposure to high energy radiation in applications such as insulation in nuclear reactors, components in medical irradiation systems and during the radiation sterilization of plastic medical equipment. Free radical processes occur both during the irradiation period and then in the post-irradiation period. Free radical scavengers such as blocked phenols are quite effective in the overall prevention of the gamma-initiated oxidative degradation of polypropylene although at the expense of strong discoloration. In this paper we compare various phenolic additives with hindered amine stabilizers (usually called HALS), both as low molecular weight and as oligomeric additives.