  Accurate measurements of K, D and B meson mixing amplitudes provide stringent
constraints in the Unitary Triangle analysis, as well as useful bounds on New
Physics scales. Lattice QCD provides a non perturbative tool to compute the
hadronic matrix elements entering in the effective weak Hamiltonian, with
errors at a few percent level and systematic uncertainties under control. I
review recent lattice results for these hadronic matrix element performed with
$N_f=2$, $N_f=2+1$ and $N_f=2+1+1$ dynamical sea quarks.
