  We present and discuss theoretical pulsational predictions concerning the
properties of Classical Cepheids. The computations have been performed for
three different chemical compositions taken as representative of Cepheids in
the Magellanic Clouds and in the Galaxy. The resulting PL relations are
significantly dependent on metallicity, with the amplitude of the metallicity
effect decreasing at the longer wavelength. At variance with several empirical
suggestions appeared in the literature, we find that at fixed period the
metal-rich pulsators should be fainter than the metal-poor ones. Tight
Period-Luminosity-Color relations are derived for both visual and near-infrared
photometric bands. We present a preliminary use of our relations to evaluate
the distance modulus of the Magellanic Clouds.
