Measurements of compressive stress relaxation for molded polytetrafluoroethylene were carried out at different temperatures over the range 60-150°C., a t 5°C. increments under a small strain (less than 0.3y0). By the application of the so-called Ferry's reduction method, three master curvea were obtained with good overlapping from a series of stress relaxation curvea obtained a t different temperatures for the same specimen. This polymer has two temperatures a t which the three master curves crow and the reduction method becomes entirely inapplicable. Those two temperatures are about 80 and 100°C. It may be concluded that this polymer has two firsborder transitions at about 80 and lOO"C., and the states above and below these temperatures are quite different, as in the case of the transition observed for this polymer a t about 2OoC., which has been confirmed to be a firsborder transition in crystal structure. The reduction factors aT at different temperatures were plotted in logarithmic scale against the reciprocals of the absolute temperatures. From the slope of those three log aT vs. l / T curves, the diagrams of the apparent activation energy vs. temperature were obtained. There were two sharp maxima at about 120 and 130°C. in the diagram, where this polymer also has two irregular changes in other viscoelastic properties. It is conceivable that these changes a t 120 and 130°C. are second-order transitions occurring in the amorphous region of the polymer.