We review some recent theoretical results on rare kaon decays. Particular attention is devoted to find Standard Model tests. This is theoretically easy in $K\to ����\bar��$, while a careful study of the long distance contributions is needed for $K_{L}\to ��^{0}e% \bar{e}$, $K_{L}\to ��\bar��$ and $K\to ������$

11 pages Latex file, no figures;Invited plenary talk at the 3rd International Conference on B Physics and CP Violation (BCONF99), Taipei, Taiwan, 3-7 Dec 1999