Calculation of the s-d self-energy and its contribution to the K0-->vacuum amplitude

The off-diagonal quark self-energy matrix element corresponding to s-->d conversion is calculated exactly in the unitary gauge. Its contribution to the K⁰-->vacuum amplitude is estimated and is found to be too small to explain the ∆I=1/2 rule in K-->2π decays. Applying pion PCAC, the K_L-->π⁰ amplitude is also estimated, and its application to K_L-->γγ discussed.