  Phenomenological issues of the CP violation in the quark sector of the
Standard Model are discussed. We consider quark mixing in the SM, standard and
Wolfenstein parametrization of the $CKM$ mixing matrix and unitarity triangle.
We discuss the phenomenology of the CP violation in $K^{0}_{L}$ and $B_{d}^{0}
(\bar B_{d}^{0})$-decays. The standard unitarity triangle fit of the existing
data is discussed. In appendix A we compare the $K^{0}\leftrightarrows \bar
K^{0}$, $B_{d,s}^{0}\leftrightarrows \bar B^{0}_{d,s}$ etc oscillations with
neutrino oscillations. In Appendix B we derive the evolution equation for
$M^{0}- \bar M^{0}$ system in the Weisskopf-Wigner approximation.
