  This is a pedagogical review of some selected topics of CP and T violation in
the decays of K mesons. Diagonalization of the quark mass matrix and the
emergence of the complex phase in both the standard and the left--right
symmetric models is considered in great detail. Prominence is given to a
correct definition of the CP-violating quantities: $\epsilon, \epsilon'$ {\it
etc.} (with due regard for the Wu--Yang phase convention) and to formulation of
the time-reversal invariance criterion in the elementary particle physics. A
particular attention has been concentrated on theoretical evaluation of the
parameters $\epsilon$ and $\epsilon'$ and the CP- and T-violating asymmetries
in the decays $K \to \mu\nu\gamma$ and $K \to 3\pi$.
