  We present some results of an on-going project aimed at studying a sample of
Galactic HII regions ionized by a single massive star to test the predictions
of modern generation stellar atmosphere codes in the H Lyman continuum. The
observations collected for this study comprise the optical spectra of the
corresponding ionizing stars, along with imaging and long-slit spatially
resolved nebular observations. The analysis of the stellar spectra allows to
obtain the stellar parameters of the ionizing star, while the nebular
observations provide constraints on the nebular abundances and gas
distribution. All this information is then used to construct tailored
photoionization models of the HII regions. The reliability of the stellar
ionizing fluxes is hence tested by comparing the photoionization model results
with the observations in terms of the spatial variation across the nebula of an
appropriate set of nebular line ratios.
