  Results concerning the dependence of photometric and radial velocity
amplitudes on metallicity are presented based on about 200 Galactic classical
Cepheids pulsating in the fundamental mode. The Galactic distribution of the
[Fe/H] value of Cepheids is also studied. We show that the photometric
amplitude ratio $A_\mathrm{I}/A_\mathrm{V}$ is independent of metallicity. The
observed dependence of this ratio on the pulsation period does not correspond
to the theoretical predictions.
