Towards Precise Determinations of the CKM Matrix without Hadronic Uncertainties

We illustrate how the measurements of the CP asymmetries in B 0 -decays together with a measurement of Br(KL ! π ◦ ν¯) or Br(K + ! π + ν¯) and the known value of | Vus | can determine all elements of the Cabibbo-Kobayashi-Maskawamatrix essentially without any hadronic uncertainties. An analysis using the ratio xd/xs of Bd ¯ Bd to Bs ¯ Bs mixings is also presented.