  The decay $b\to s\nu\bar{\nu}$ is discussed in the minimal supersymmetric
standard model with general flavor mixing for squarks, at large $\tan\beta$. In
this case, in addition to the chargino loop contributions which were analyzed
in previously studies, $\tan\beta$-enhanced contributions from the gluino and
charged Higgs boson loops might become sizable compared with the standard model
contribution, at least in principle. However, it is demonstrated that the
experimental bounds on the new physics contributions to the radiative decay
$b\to s\gamma$ should strongly constrain these contributions to $b\to
s\nu\bar{\nu}$, especially on the gluino contribution. We also briefly comment
on a possible constraint from the $B_s\to\mu^+\mu^-$ decay.
