  $B^0$ mixing measurements from the Tevatron Run I data are reported. These
include time-integrated measurements of the average mixing parameter
$\bar{\chi}$, six time-dependent oscillation measurements of $\Delta m_d$, and
a time-dependent limit on $\Delta m_s$. Such measurements provide constraints
on CKM matrix elements. A sample of $B^0/\bar{B}{^0} \to J/\psi K^0_S$ decays
is used to directly measure the CP-violation parameter $\sin(2\beta)$. This
value agrees well with indirect constraints on the CKM matrix.
