A light bottom squark in the MSSM

We study the compatibility of a light bottom squark M-(b) over tilde < O (1 0 GeV) in the unconstrained MSSM. We consider the one-loop radiative correc tions which are large for a heavy gluino (> O (150 GeV)). We then consider the renormalization group ow up to the Grand Unified scale. For most region s of the parameter space with a light sbottom we find directions in the sca lar potential which are unbounded from below. Only a small window in gluino mass and tan fi is consistent with all bounds. This is alleviated by a lig ht gluino, which is however only marginally experimentally allowed.