  The inclusive radiative $B$-decay is a sensitive probe of new physics,
especially if related to the virtual exchange of a charged Higgs boson.
Supersymmetric models provide a particularly interesting example. In the limit
of exact supersymmetry, BR($b \to s\gamma$)~=~0, due to the vanishing of any
magnetic-moment transition operator. We illustrate the impact of this
constraint for realistic values of the supersymmetry-breaking parameters.
