  The recent release of improved lattice data has revived again the interest on
precise theoretical calculations of the direct CP-violation ratio
$\varepsilon'/\varepsilon$. We present a complete update of the Standard Model
prediction [1,2], including a new re-analysis of isospin-breaking corrections
which are of vital importance in the theoretical determination of this
observable. The Standard Model prediction, $\mathrm{Re} (\epsilon'/\epsilon) =
(14\pm 5)\cdot 10^{-4}$, turns out to be in good agreement with the
experimental measurement.
