  We present lattice calculations of kaon matrix elements with domain wall
fermions. Using lattices with beta=5.85, 6.0, and 6.3, we estimate B_K(approx 2
GeV)=0.628(47) in quenched QCD which is consistent with previous calculations.
At beta=6.0 and 5.85 we find the ratio f_K/m_rho in agreement with the
experimental value, within errors. These results support expectations that O(a)
errors are exponentially suppressed in low energy (E<< a^{-1}) observables, and
indicate that domain wall fermions have good scaling behavior at relatively
strong couplings. We also demonstrate that the axial current numerically
satisfies the lattice analog of the usual continuum axial Ward identity.
