Semileptonic Decays: an Update down under *

Heavy-meson semileptonic decays calculations on the lattice are reviewed. The focus is upon obtaining reliable matrix elements. Errors that depend upon the lattice spacing, a, are an important source of systematic error. Full O(a) improvement of matrix elements for arbitrary-mass four-component quarks is discussed. With improvement, bottom-quark matrix elements can be calculated directly using current lattices. Momentum dependent errors for O(a)-improved quarks and statistical noise limit momenta to around 1GeV/c with current lattices. Hence, maximum recoil momenta can be reached for D decays while only a fraction of the maximum recoil momentum can be reliably studied for the light-meson decay modes of the B. Differential decay rates and partial widths are phenomenologically important quantities in B decays that can be reliably determined with present lattices.