Weak interactions of kaons from lattice QCD

The methods of lattice QCD and available computer resources are now sufficient that predictions for many of the Standard Model properties of kaons can be made from first principles with accurately bounded uncertainties. We discuss two relatively new areas where lattice methods are having or will soon have a large impact: calculation of the two complex amplitudes A(0) and A(2) describing the decay of the kaon into two-pions with I = 0 and 2 and calculation of long-distance contributions to second-order electro-weak processes including the K-L-K-S mass difference Delta M-K, the CP-violating parameter epsilon(K) and certain rare kaon decays.