The limit surface sections by longitudinal and deviatoric planes have been plotted for 3 polymeric polyoxy-methylene (POM), polytetrfluoroethylene (PTFE) and polypropylene (PP) on the basis of experimental data on tension, compression and torsion under conditions of hydrostatic compression. Some yield criteria are considered with the account taken of the hydrostatic pressure influence. The disturbance in the convexity of the limit curves for PTFE and PP has been noticed which is associated with structural changes in the material caused by the increase in pressure.