The polymerization of vinyl monomers can be initiated by heat, ultraviolet radiation, and various catalysts. More recently, ionizing radiation has been shown to effectively initiate vinyl polymerization. However, polymerization in the solid state by ionizing radiation is not reported in the literature, although several papers have been published that describe briefly the thermal polymerization of divinyldiphenyl, Leuch's anhydride and in greater detail the peroxide catalyzed polymerization of acetaldehyde. The purpose of this note is to describe some experiments which demonstrate that crystalline acrylamide undergoes polymerization upon irradiation with γ-rays from an intense Co-60 source. Below its melting point the monomer shows little or no tendency to polymerize thermally.