  We present results on the B-parameters $B_K$, $B^{3/2}_7$ and $B^{3/2}_8$, at
$\beta=6.0$, with the tree-level Clover action. The renormalization of the
complete basis of dimension-six four-fermion operators has been performed
non-perturbatively. Our results for $B_K$ and $B^{3/2}_7$ are in reasonable
agreement with those obtained with the (unimproved) Wilson action. This is not
the case for $B^{3/2}_8$. We also discuss some subtleties arising from a
recently proposed modified definition of the B-parameters.

High Energy Physics - Lattice