  The relationship between the integrated H$\beta$ line luminosity and the
velocity dispersion of the ionized gas of HII galaxies and giant HII regions
represents an exciting standard candle that presently can be used up to
redshifts z ~ 4. Locally it is used to obtain precise measurements of the
Hubble constant by combining the slope of the relation obtained from nearby ($z
\leq $ 0.2) HII galaxies with the zero point determined from giant HII regions
belonging to an `anchor sample' of galaxies for which accurate
redshift-independent distance moduli are available. We present new data for 36
giant HII regions in 13 galaxies of the anchor sample that includes the
megamaser galaxy NGC 4258. Our data is the result of the first four years of
observation of our primary sample of 130 giant HII regions in 73 galaxies with
Cepheid determined distances. Our best estimate of the Hubble parameter is
$71.0\pm2.8(random)\pm2.1(systematic)$ km /s Mpc This result is the product of
an independent approach and, although at present less precise than the latest
SNIa results, it is amenable to substantial improvement.
