  We address the compatibility of a light sbottom (mass $2\sim 5.5 \gev$) and a
light gluino (mass $12\sim 16 \gev$) with electroweak precision measurements.
Such light particles have been suggested to explain the observed excess in the
$b$ quark production cross section at the Tevatron. The electroweak observables
may be affected by the sbottom and gluino through the SUSY-QCD corrections to
the $Zbb$ vertex. We examine, in addition to the SUSY-QCD corrections, the
electroweak corrections to the gauge boson propagators from the stop which are
allowed to be light from the SU(2)$_L$ symmetry. We find that this scenario is
strongly disfavored from electroweak precision measurements unless the heavier
sbottom mass eigenstate is lighter than $180\gev$ and the left-right mixing in
the stop sector is sufficiently large. This implies that one of the stops
should be lighter than about $98\gev$.
