We have measured 158 μm [CII] line emission from a sample of thirteen gas rich galaxies. The new data are combined with the previous sample of six infrared bright galaxies of Crawford et al. 1985. The [CII] line is bright in all of the galaxies detected amounting to between .1 and 2% of the total nuclear far-infrared (FIR) luminosity, and is therefore one of the primary gas coolants in these regions. The [CII] emission arises from warm (T-300 K), dense (NH∼103→104cm−3) photodissociated gas at the interface regions between giant molecular clouds and ionized gas regions, and is a very sensitive indicator of starformation activity. The integrated [CII] to the 12CO line intensity ratio is constant for starburst galaxies and star formation regions in our own galaxy. This suggests that much of the observed 12CO line radiation from starburst galaxies arises in the warm, (Tex>50 K), molecular gas immediately interior to these photodissociation regions, and not from the cold disk molecular cloud component as is commonly assumed. For the non-starburst galaxies in our sample, the line intensity ratio varies significantly from galaxy to galaxy but is always significantly less than the starburst value, in support of this model. The integrated line intensity ratios may thus be used as a sensitive probe of the physical conditions of the molecular gas in galaxies.