  B physics represents a privileged place to look for supersymmetry (SUSY)
through its virtual effects. Here we discuss rare B decays ($b \to s \gamma$,
$b \to s g$, $b \to s l^{+} l^{-}$) and $B-\bar{B}$ oscillations in the context
of low-energy SUSY. We outline the variety of predictions that arise according
to the choice of the SUSY extension ranging from what we call the ``minimal"
version of the MSSM to models without flavour universality or with broken
R-parity. In particular, we provide a model-independent parameterization of the
SUSY FCNC effects which is useful in tackling the problem in generic low-energy
SUSY. We show how rare B physics may be complementary to direct SUSY searches
at colliders, in particular for what concerns extensions of the most
restrictive version of the MSSM.
