  We analyze the evolution of oxygen abundance radial gradients resulting from
our chemical evolution models calculated with different prescriptions for the
star formation rate (SFR) and for the gas infall rate, in order to assess their
respective roles in shaping gradients. We also compare with cosmological
simulations and confront all with recent observational datasets, in particular
with abundances inferred from planetary nebulae. We demonstrate the critical
importance in isolating the specific radial range over which a gradient is
measured, in order for their temporal evolution to be useful indicators of disk
growth with redshift.
