  Dyson-Schwinger equation (DSE) studies show that the b-quark mass-function is
approximately constant, and that this is true to a lesser extent for the
c-quark. These observations provide the basis for a study of the leptonic and
semileptonic decays of heavy pseudoscalar mesons using a ``heavy-quark'' limit
of the DSEs. When exact, this limit reduces the number of independent form
factors. Semileptonic decays with light mesons in the final state are also
accessible because the DSEs provide a description of light-quark propagation
characteristics and light-meson structure. A description of B-meson decays is
straightforward, however, the study of decays involving the D-meson indicates
that c-quark mass-corrections are quantitatively important.
