This article contains results of experimental research of polytetrafluoroethylene (PTFE) deformation and creep under linear and plane stresses. During the tests predetermined values of real stresses considering current deformation were constant. The equation of mechanical states considering instant elastic, viscoelastic, instant plastic and viscoplastic components of total deformation was obtained. The equation is used for the description of PTFE deformations (F-4, F-4D, F-4D0) under stationary and non-stationary cyclic loads in flat stress condition with an application of material constant volume condition, condition of similarity of deviators of stresses and deformations and with the input of parameters which are functions of the form of stress deviators. The results of PTFE creep investigation under real stresses reaching ultimate values are relevant and unique.