  The sensitivity of THERA to different models of "new physics" has been
studied, both for the contact interaction approximation and for the resonance
production. For contact interaction models conserving parity, scales up to
about 18 TeV can be explored at THERA, extending considerably beyond the
existing bounds. Significant improvement of existing limits is also expected
for models with large extra dimensions. Effective Plank mass scales up to about
2.8 TeV can be probed. THERA will be the best machine to study leptoquark
properties, for leptoquark masses up to about 1 TeV. It will be sensitive to
the leptoquark Yukawa couplings down to lambda ~ 0.01.
