  We study both CP conserving and violating contributions to the decay
$K_L\to\pi^+\pi^-\nu\bar{\nu}$. We find that the decay branching ratio is
dominated by the CP conserving part. In the standard CKM model, we estimate
that for $m_t\sim 174\ GeV$, the branching ratio due to the CP conserving
(violating) contributions can be as large as $4.4 \times 10^{-13}$ ($1.0\times
10^{-14}$).
