  We conduct a Galactic census of Giant HII regions, based on the all sky 6cm
dataset of Kuchar & Clark, plus the kinematic distances obtained by Russeil.
  From an inspection of mid-IR Mid-course Space Experiment (MSX) and far-IR
IRAS Sky Survey Atlas images we identify a total of 56 GHII regions in the
Milky Way, of which 15% (65%) can be seen at optical (near-IR) wavelengths.The
mid to far-IR fluxes from each GH {\sc ii} region are measured, and sample the
thermal emission from the ubiquitous dust present within the exciting clusters
of OB stars, arising from the integrated luminosity of the hot stars heating
the cluster dust, for which we obtain log L(IR)=5.5-7.3 L_sun. The mid-IR
21micron spatial morphology is presented for each GHII region, and often
indicates multiple emission sources, suggesting complicated cluster formation.
IR colour-colour diagrams are presented, providing information about the
temperature distribution and optical depth of the dust. For the clusters of our
study, the dust is not optically thick to all the stellar radiation, thus the
measured infra-red luminosity is lower than the L(bol). As the dust environment
of a cluster begins to dissipate, the thermal emission and its optical depth
ought to decrease even before the stars appreciably evolve. We see evidence of
this in our empirical relationship between the integrated IR and Lyman
continuum luminosities.
