  We follow the chemical evolution of the Galaxy for the s elements using a
Galactic chemical evolution (GCE) model, as already discussed by Travaglio et
al. (1999, 2001, 2004), with a full updated network and refined asymptotic
giant branch (AGB) models. Calculations of the s contribution to each isotope
at the epoch of the formation of the solar system is determined by following
the GCE contribution by AGB stars only. Then, using the r-process residual
method we determine for each isotope their solar system r-process fraction, and
recalculate the GCE contribution of heavy elements accounting for both the s
and r process. We compare our results with spectroscopic abundances at various
metallicities of [Sr,Y,Zr/Fe], of [Ba,La/Fe], of [Pb/Fe], typical of the three
s-process peaks, as well as of [Eu/Fe], which in turn is a typical r-process
element. Analysis of the various uncertainties involved in these calculations
are discussed.
