  We present the matrix elements for the semileptonic kaon decays
$K_{l2\gamma}$ , $K_{l2l^+l^-}$, $K_{l2l'^+l'^-}$,$K_{l3}$, $K_{l3\gamma}$ and
$K_{l4}$ at next-to-leading order, and $K_{e5}$ at leading order in Chiral
Perturbation Theory and compare the predictions with experimental data. For
$K_{l4}$ decays we estimate yet higher orders in order to reduce theoretical
uncertainties in the comparison with the data. Monte Carlo event generators are
used to calculate the corresponding rates at DA$\Phi$NE. We discuss the
possibilities to improve our knowledge of the low-energy structure of the
Standard Model at this and similar machines.
