  We report progress on a non-perturbative calculation of the light quark mass
renormalization factor Z_m, using dynamical Asqtad fermions. This quantity is
used to determine the light quark masses in the conventional MS-bar scheme.
Such a non-perturbative determination of Z_m removes uncertainties due to
truncation of its perturbative expansion, currently known to two loops. These
calculations have been carried out using publicly available MILC lattices with
spacings of approximately 0.125 and 0.09 fm.
