  A method parametrizing all inelastic final state interactions (FSI) in $B\to
PP$ decays is presented ($P$ - pseudoscalar meson). The method explicitly shows
how rescattering leads to the replacement of the short-distance amplitudes with
the effective quark diagram amplitudes, and how it affects the extraction of
the unitarity triangle angle $\gamma $ from the data. It is furthermore pointed
out that the size of FSI effects cannot be determined from $B^0_d \to K^+ K^-$
decays in a satisfactory way. The case of SU(3)-violating FSI is also
discussed. When fits to the branching ratios of all $B \to PP$ decays are
performed with all inelastic FSI included, the extracted value of $ \gamma $ is
shifted down by some $20^o-30^o$ when compared to the no-FSI analyses, and
becomes consistent with the Standard Model value of $ 65^o \pm 7^o$.
