  The aim of this work is to present our new series of chemical evolution
models computed for spiral and low mass galaxies of different total masses and
star formation efficiencies. We analyze the results of models, in particular
the evolution of the radial gradient of oxygen abundance. Furthermore, we study
the role of the infall rate and of the star formation history on the variations
of this radial gradient. The relations between the O/H radial gradient and
other spiral galaxies characteristics as the size or the stellar mass are also
shown. We find that the radial gradient is mainly a scale effect which
basically does not change with the redshift (or time) if it is measured within
the optical radius. Moreover, when it is measured as a function of a normalized
radius, show a similar value for all galaxies masses, showing a correlation
with a dispersion around an average value which is due to the differences star
formation efficiencies, in agreement with the idea of an universal O/H radial
gradient
