  We present an overview of the loop corrections to the mass difference $\Delta
m_{B_d^0}/ m_{B_d^0}$ within the minimal supersymmetric standard model. We
include the complete mixing matrices of the charginos and neutralinos as well
as of the scalar partners of the left and right handed third generation quarks.
We show that the SUSY contribution to the mass difference in the $B_d^0$ system
is comparable to the Standard Model one and can be even larger for the charged
Higgs contribution and for a certain supersymmetric parameter space.
