  The problem of calculation of the enhancement factor due to the strong pion
final state interaction is reexamined in the light of recent interest in
understanding of the origine of the $\Delta I=1/2$ rule and calculations of the
CP violation parameter $\epsilon^{\prime}/\epsilon$. It is shown that the
traditional method of calculating the \emph{absolute} enhancement factor is
model dependent, while the method of relating $K \to 2\pi$ amplitude to the
$K-\pi$ matrix element using Current Algebra is on a safer ground.
