  We have imaged a sample of 20 face-on spiral galaxies in H\alpha and in the
near-IR K-band (2.2 microns), in order to determine the location and strength
of star formation with respect to perturbations in the old stellar population.
We found that star formation rates are significantly enhanced near K-band arms.
If K-band light is dominated by emission from old stars, this shows that
density waves trigger star formation. However, no significant correlation was
found between the global underlying disk properties of spiral galaxies and
their total star formation rates.
