  A brief review is made of some of the experimental signatures that may be
associated to a certain class of extensions of the standard model. The material
of these lectures is divided into two sections. After briefly sketching the
present observational status of the neutrino masses I consider various schemes
of neutrino mass generation, including those which are motivated by present
experimental hints from solar and atmospheric neutrinos, as well as
cosmological data on the amplitude of primordial density fluctuations. Then
some of the physics motivations and potential of various extensions of the
standard model related to the electroweak breaking sector, such as
supersymmetry, and extensions of the gauge boson sector are reviewed. The new
signatures associated with both types of extension may all be accessible to
experiments performed either at accelerators or at underground installations.
The complementarity between these two approaches in the search for signals
beyond the standard model is most vividly manifest in the field of neutrino
physics.
