  Physical models of Type Ia supernovae (SN Ia) that do not depend on secondary
calibrators have indicated that the Hubble Constant must be about 65 km/s/Mpc
for well over a decade with the range of uncertainty shrinking with the
sophistication of the models. This estimate is in good agreement with those
based on HST observations of Cepheid variables and with purely empirical
methods based on SN Ia calibrated with Cepheids. The prospects of progress in
understanding the physics of the explosion of SN Ia and of their application to
measure other cosmological parameters is reviewed. Despite the rather complex
nature of their atmospheres, SN Ia may give a more reliable estimate of
distances than Type II. The latter depend on remaining uncertainties in the
scattering atmospheres, the helium abundance and possible systematic effects
due to distortions of the envelope that will not average out even in a large
sample.
