  We combine the radio continuum images from the NRAO VLA Sky Survey with the
CO-line observations from the extragalactic CO survey of the Five College Radio
Astronomy Observatory to study the relationship between molecular gas and the
star formation rate within the disks of 180 spiral galaxies at 45" resolution.
We find a tight correlation between these quantities. On average, the ratio
between the radio continuum and the CO emission is constant, within a factor of
3, both inside the same galaxy and from galaxy to galaxy. The mean star
formation efficiency deduced from the radio continuum corresponds to convert
3.5% of the available molecular gas into stars on a time scale of 10^8 yr and
depends weakly on general galaxy properties, such as Hubble type or nuclear
activity. A comparison is made with another similar analysis performed using
the H_alpha luminosity as star formation indicator. The overall agreement we
find between the two studies reinforces the use of the radio luminosity as star
formation rate indicator not only on global but also on local scales.
