  We investigate how a different calibration of the Cepheid Period-Luminosity
(PL) relation taking into account the metallicity corrections, affects the
absolute magnitude calibration of Supernovae (SNe) Ia and, in turn, the
determination of the Hubble constant H_0. We exploit SN Ia light curves from
literature and previously unpublished data, to build the M_B -- Delta m_{15}(B)
relation and we calibrate the zero point by means of 9 type Ia SNe with Cepheid
measured distances. This relation was then used to build the Hubble diagram and
in turn to derive H_0. In the attempt to correct for the host galaxy
extinction, we found that the data seems to suggest a value for the total to
selective absorption ratio, R_B=3.5, which is smaller than the standard value
for our own Galaxy R_B=4.315. Depending on different metallicity corrections
for the Cepheids P-L relation, values of R_B and SN sample selection criteria,
we found that the values of the Hubble constant H_0 is in the range 68--74 km
s^{-1} Mpc^{-1}, with associated uncertainties of the order of 10%. Unpublished
photometry is also presented for 18 SNe of our sample (1991S, 1991T, 1992A,
1992K, 1993H, 1993L, 1994D, 1994M, 1994ae, 1995D, 1995ac, 1995bd, 1996bo,
1997bp, 1997br, 1999aa, 1999dk, 2000cx), which are the results of a long
standing effort for supernova monitoring at ESO - La Silla and Asiago
Observatories.
