The effects of heavy elements abundance on theoretical observables is studied for both fundamental and first overtone RR Lyrae pulsators at fixed mass and luminosity level. Nonlinear models have been computed adopting three different metal content. It has been found that the bolometric amplitude of first overtone pulsators decreases as metallicity increases, whereas for fundamental pulsators the amplitude is positively correlated with the metal abundance.

postscript file of 14 pages and 4 figures; for any problem please write to bono@oat.ts.astro.it