A method is presented of measuring the equivalent nitrogen vapor pressure of polymeric materials over a range of temperatures. It is found that, for the range of temperatures investigated (300–450°K), the vapor pressure‐temperature characteristics of the polymeric materials studied are described by the empirical relationlogP=A−B/T.The values of the constantsAandBin this equation are determined for a number of materials including nylon, Teflon, saran, polyethylene, and mylar.