  I discuss three different topics concerning the chemical evolution of the
Milky Way (MW). 1) The metallicity distribution of the MW halo; it is shown
that this distribution can be analytically derived in the framework of the
hierarchical merging scenario for galaxy formation, assuming that the component
sub-haloes had chemical properties similar to those of the progenitors of
satellite galaxies of the MW. 2) The age-metallicity relationship (AMR) in the
solar neighborhood; I argue for caution in deriving from data with important
uncertainties (such as the age uncertainties in the Geneva-Kopenhaguen survey)
a relationship between average metallicity and age: derived relationships are
shown to be systematically flatter than the true ones and should not be
directly compared to models. 3) The radial mixing of stars in the disk, which
may have important effects on various observables (scatter in AMR, extension of
the tails of the metallicity distribution, flatenning of disk abundance
profiles). Recent SPH + N-body simulations find considerable radial mixing, but
only comparison to observations will ultimately determine the extent of that
mixing.
