  We present results for the leptonic decays of heavy-light mesons in the
quenched approximation and a preliminary result for f_Ds with dynamical
fermions for Nf=2. We examine the systematic effects of extrapolating the decay
constants from the charm to the bottom quark mass, and find this extrapolation
to be under control. We present a preliminary result for f_Ds{Nf=2} and compare
to f_Ds{Nf=0} matched to have the same lattice spacing set by the Sommer scale,
r0. We find no significant difference.
