  We discuss the theory prediction of epsilon_K and the rare K -> pi nu nu-bar
decays and review the structure and current status of higher-order
contributions to these flavour changing processes in the standard model in some
detail. This includes the next-to-next-to-leading order QCD calculation to the
charm quark contribution to K+ -> pi+ nu nu-bar and to the charm-top quark
contribution to epsilon_K. Electroweak corrections to the rare kaon decays are
also discussed.
