  Determinations of $\vud$ and $\vus$ along with their implications for the
unitarity test $\vud^2+\vus^2+\vub^2=1$ are discussed. The leading two loop
radiative corrections to neutron $\beta$-decay are evaluated and used to derive
a refined relationship $\vud^2 \tau_n (1+3g_A^2)=4908(4)$sec. Employing $\vud
=0.9740(5)$ from superallowed nuclear decays and the measured neutron lifetime
$\tau_n = 885.7(7)$sec, leads to the precise prediction $g_A=1.2703(8)$ which
is compared with current direct experimental values. Various extractions of
$\vus$ are described and updated. The long accepted Particle Data Group value
of $\vus$ 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.
