  We reinvestigate the leading QCD corrections to the radiative decay $b \to s
\gamma for supersymmetric extensions of the Standard Model. Although the major
contributions to the corrections originate from the running of the effective
Lagrangian from the W scale down to the $b$ scale, additional corrections are
expected from large mass splittings between the particles running in the loops,
as well as from integrating out heavy particles at scales different from the W
mass. The calculation is performed in the framework of effective field
theories.
