  The minimal supersymmetric standard model (MSSM) with universal soft breaking
terms has a negligible effect on the rare $c\to u\gamma$ decay rate. We
therefore study a general model with non-universal soft breaking terms
constrained by vacuum stability and the experimental upper bound on the mass
difference of the neutral charm mesons. It turns out that gluino exchange can
enhance the standard model rate by up to two orders of magnitudes; in contrast,
the contributions from charginos and neutralinos remain at least an order of
magnitude below the QCD corrected standard model rate.
