  The Spitzer IRS high resolution spectra of about 90 Seyfert galaxies from the
12um Galaxy Sample are presented and discussed. These represent about 70% of
the total complete sample of local Seyfert galaxies. The presence of starburst
components in these galaxies can be quantified by powerful mid-IR diagnostics
tools (i.e. 11.25um PAH feature equivalent width and the H_2 emission line
intensity) as well as the AGN dominance can be measured by specific fine
structure line ratios (e.g. [NeV]/[NeII], [NeV]/[SiII], etc.). The observed
line ratios are compared to the results of semianalytical models, which can be
used to compute the AGN and starburst contributions to the total luminosity of
the galaxies. The results are also discussed in the light of unification and
evolution models.

Astrophysics of Galaxies;Cosmology and Nongalactic Astrophysics