  The $b\rightarrow s+ \gamma$ decay is a powerful tool for testing models of
new physics because the new physics diagrams enter in the same loop order as
the Standard Model ones. The current experimental and theoretical status of
this decay is reviewed. Predictions based on the minimal supergravity model
(MSGM) in the leading order (LO) are discussed. It is shown that results are
sensitive to the value of $m_{t}$ and $\alpha_{G}$. The current experimental
value for the $b\rightarrow s + \gamma$ rate already very likely eliminates
part of the SUSY parameter space when both $m_{o}$ and $m_{\tilde{g}}$ are
small and when $A_{t}$ and $\mu$ have the same sign. Dark matter detection
rates for $\tilde{Z}_{1}$ cold dark matter for $\mu <0$ are only minimally
affected by the current data, as are proton decay predictions for models
consistent with current proton lifetime and $\tilde{Z}_{1}$ relic density
bounds. [\dag Invited talk at ``Physics From Planck Scale to Electroweak
Scale'', Warsaw, Sept. 21-24, 1994].
