  The motivations for low-energy supersymmetry and the main features of the
minimal supersymmetric extension of the Standard Model are reviewed. Possible
non-minimal models and the issue of gauge coupling unification are also
discussed. Theoretical results relevant for supersymmetric particle searches at
present and future accelerators are presented, with emphasis on the role of a
proposed $\epem$ collider with $\sqrt{s}
  = 500 \gev$. In particular, recent results on radiative corrections to
supersymmetric Higgs boson masses and couplings are summarized, and their
implications for experimental searches are discussed in some detail. (Plenary
talk at the Workshop on Physics and Experiments with Linear Colliders,
Saariselk\"a, Lapland, Finland, 9--14 September 1991)
