  In view of the extreme smallness of $\Delta S = 2$ transitions of $B$ meson
in the Standard Model, we consider their occurence in several extensions of it.
Thus, we analyze the three - body $B^- \to K^- K^- \pi^+$ and two - body $B^-
\to K^{*-} \barK^{*0}$, $B^- \to K^- \bar K^{0}$, $B^- \to K^{*-} \bar K^{0}$,
$B^- \to K^{-} \bar K^{*0}$ decay modes both in the Standard Model and in the
Minimal Supersymmetric Model with and without ${\cal R}$ parity conservation
and in two Higgs doublet models. All five modes are found to have a branching
ratio of the order of $10^{-13}$ in the Standard Model, while the expected
branching ratio in the different extensions vary between $10^{-9} - 10^{-6}$,
for a given reasonable choice of parameters.
