Effects of gamma radiation on the properties, such as melt viscosity, elastic modulus above the melting point, creep fracture time above the melting point, density, and the degree of crystallinity by x-ray diffraction, of polytetrafluoroethylene resin were studied. When exposed to the radiation from a Co60 gamma source, the melt viscosity falls rapidly with increasing radiation dose above 10 (to the fourth power) roentgens, and the rubber elasticity above the melting point decreases with increasing irradiation. Also, Zero Strength Time (a creep fracture time test) above the melting point decreases rapidly with irradiation above 10 (to the third power) roentgens; this behavior is attributable to the chain scission and the accompanying decrease in average molecular weight. Density was found to increase with radiation dose at doses higher than 10 (to the fourth power) roentgens; also, at 2theta = 18° peak in the X-ray diffraction pattern, which is indicative of crystallinity, increases slightly in sharpness with irradiation. These facts suggest that gamma irradiation of this polymer produces chain scission and decreases the average molecular weight, and also causes partial crystallization followed by an increase in the density in the amorphous region. Therefore, crosslinking would probably be negligible in this polymer.