Observations of two neon fine structure lines will give the absolute
neon abundance and its radial gradient in H II regions in the disk of
the spiral galaxy M 33.  This will serve as a check on the model-
dependent abundances derived from visible lines.  Nucleosynthesis
models predict that the neon abundance should track the oxygen
abundance.  If it does not, photoionization models for H II regions
or the nucleosynthesis models must be wrong.  Only ISO has the
sensitivity to observe the lines in the relatively diffuse H II
regions known in M 33, and the [Ne III] line is not observable from
the ground, aircraft, or even from balloons.