  In these notes I will review the results that have been obtained in these
last years on the computation of the number of metastable states in
infinite-range models of disordered systems. This is a particular case of the
problem of computing the exponentially large number of stationary points of a
random function. Quite surprisingly supersymmetry plays a crucial role in this
problem. A careful analysis of the physical implication of supersymmetry and of
supersymmetry breaking will be presented: the most spectacular one is that in
the Sherrington-Kirkpatrick model for spin glasses most of the stationary
points are saddles, as predicted long time ago.
