A methodology for determination of time- and temperature-dependences of stress threshold of linear-nonlinear viscoelastic transition is proposed and validated by example of uniaxial creep of epoxy resin. Energy approach is applied for characterization of the region of linear viscoelasticity (LVE) and the threshold of LVE is given in the stress-strain representation as the master curve independent of time and temperature. Time-and temperature-dependences of the stress threshold are calculated by extending LVE theory and time-temperature superposition principles (TTSP) to the energy relations. Reasonable agreement between experimental data and calculations is obtained. It is shown that number of tests required for characterization of LVE region in a wide range of test time and temperatures can be considerably reduced by applying the proposed methodology. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2187-2192, 2011