  All relevant inputs for the extraction of the CKM matrix element \vus from
\kl, \ks and \kpm decays have been measured at KLOE. From a global fit using
only KLOE results, but \ks lifetime, a value of $|\vus|\fzero = 0.2157 \pm
0.0006$ is obtained, where \fzero is the form factor parametrizing the hadronic
matrix element evaluated at zero momentum transfer. Comparison of the values of
\fVus for $K_{e3}$ and $K_{\mu3}$ modes provides a test of lepton universality
at 0.8% level of accuracy. The value $\vus/\vud=0.2323(15)$ has been obtained
from the ratio $\Gamma(K\to\mu \nu)/\Gamma(\pi\to\mu \nu)$ using KLOE
measurement of $\BR(\kpm \to \mudue)$ and lattice calculation of the ratio of
decay constants $f_K/f_{\pi}$. These results, together with $\vud =
0.97418(26)$, are compatible at 0.6$\sigma$ level with CKM matrix unitarity.
The universality of lepton and quark weak couplings can be tested and
constraints on new physics extensions of the Standard Model can be set using
these very precise measurements from kaon decays.
