  We compute several matrix elements of dimension-six four-fermion operators
and extract their B-parameters. The calculations have been performed with the
tree-level Clover action at $\beta = 6.0$. The renormalization constants and
mixing coefficients of the lattice operators have been obtained
non-perturbatively. In the $\MSbar$ renormalization scheme, at a
renormalization scale $\mu \simeq 2$ GeV, we find $B_K (B_9^{3/2}) = 0.66(11),
B_7^{3/2} = 0.72(5)$ and $B_8^{3/2} = 1.03(3)$. The result for $B_8^{3/2}$ has
important implications for the calculation of $\epsilon^\prime / \epsilon$.
