K->pi nu(nu)over-bar and high precision determinations of the CKM matrix

We investigate the future determination of the CKM matrix using theoretically clean quantities, such as B(K+ --> pi(+) <nu(nu)over bar>, B(K-L --> pi(0) <nu(nu)over bar> or sin 2 beta, sin 2 alpha as extracted from CP violation studies in B physics. The theoretical status of K --> pi <nu(nu)over bar> is briefly reviewed and their phenomenological potential is compared with that of CP asymmetries in B decays. We stress the unique opportunities provided by measuring the CP-violating rare decay K-L --> pi(0) <nu(nu)over bar>. It is pointed out that this mode is likely to offer the most precise determination of Im V-ts*C-td and the Jarlskog parameter J(CP), the invariant measure of CP violation in the standard model.