  The enrichment of Pb in the Galaxy is followed in the framework of a detailed
model of Galactic chemical evolution that already proved adequate to reproduce
the chemical enrichment of O and of the elements from Ba to Eu. The stellar
yields are computed through nucleosynthesis calculations in the Asymptotic
Giant Branch (AGB) phase of low- and intermediate-mass stars, covering a wide
range of metallicities. The physical parameters of the stellar structure were
derived from full stellar evolutionary models previously computed. We show that
low-mass AGB stars are the main producers of Pb in the Galaxy, with a complex
dependence on metallicity and a maximum efficiency at [Fe/H] ~ -1. Our
calculations succeed in reproducing the abundances of Pb isotopes in the solar
system: the role attributed by the classical analysis of the s-process to the
'strong component', in order to explain more than 50% of solar 208Pb, is
actually played by the high production of Pb in low-mass and low-metallicity
AGB stars. We then follow the Galactic chemical evolution of Pb isotopes and
give our expectations on the s-process contribution to each of them at the
epoch of the solar system formation. Finally, we present new spectroscopic
estimates of Pb abundance on a sample of field stars and compare them, together
with a few other determinations available, with the predicted trend of [Pb/Fe]
in the Galaxy.
