  Far-ultraviolet (900-1200A) spectral synthesis of nine giant extragalactic
HII regions in M 33 and M 101 is performed to study their massive stellar
content. Several parameters are quantified, predicted, and compared to the
literature: age, stellar mass, IMF slope, number of O-type and Wolf-Rayet
stars, Halpha and 5500A continuum fluxes. The results of this particular
technique are consistent with other methods and observations. This work shows
that a total stellar mass of a few 10^3 Msun is needed to populate the IMF bins
well enough at high masses to obtain accurate results from the spectral
synthesis technique in the far-ultraviolet. A flat IMF slope seems to
characterize better the stellar line profiles of these objects, which is likely
the first sign of a small number statistic effect on the IMF. Finally, the HII
region NGC 5461 is identified as a good candidate for hosting a second
generation of stars, not yet seen at far-ultraviolet wavelengths.
