  We study the evolution of nitrogen resulting from a set of spiral and
irregular galaxy models computed for a large number of input mass radial
distributions and with various star formation efficiencies. We show that our
models produce a nitrogen abundance evolution in good agreement with the
observational data. In particular, low N/O values for high-redshift objects,
such as those obtained for Damped Lyman Alpha galaxies can be obtained with our
models simultaneously to higher and constant values of N/O as those observed
for irregular and dwarf galaxies, at the same low oxygen abundances $\rm
12+log(O/H) \sim 7$ dex. The differences in the star formation histories of the
regions and galaxies modeled are essential to reproduce the observational data
in the N/O-O/H plane.
