  Symmetry restoration processes during the non-equilibrium stage of
``preheating'' after inflation is studied. It is shown that symmetry
restoration is very efficient when the majority of created particles are
concentrated at energies much smaller than the temperature $T$ in equilibrium.
The strength of symmetry restoration measured in terms of the equivalent
temperature can exceed $T$ by many orders of magnitude. In some models the
effect can be equivalent to that if the temperature of instant reheating would
be close to the Planck scale. This can have an important impact on GUT and
axion models.
