Precision measurements and CKM unitarity

Determinations of |V-ud| and |V-us| along with their implications for the unitarity test |V-ud|(2)+|V-us|(2)+|V-ub|(2)=1 are discussed. The leading two-loop radiative corrections to neutron beta decay are evaluated and used to derive a refined relationship |V-ud|(2)tau(n)(1+3g(A)(2))=4908(4) s. Employing |V-ud|=0.9740(5) from superallowed nuclear decays and the measured neutron lifetime tau(n)=885.7(7) s leads to the precise prediction g(A)=1.2703(8) which is compared with current direct experimental values. Various extractions of |V-us| are described and updated. The long accepted Particle Data Group value of |V-us| from fitted K-e3 decay rates suggests a deviation from CKM unitarity but it is contradicted by more recent experimental results which confirm unitarity with good precision. An outlook for possible future advances is given.