  V-band luminosity functions have been obtained for the upper main-sequence,
sub-giant branch and red giant branch of 18 galactic globular clusters from HST
data. A comparison with four sets of theoretical models has been performed. In
contrast with what was found in several previous works, a Good general
agreement has been found between the observed and theoretical LF at any
metallicity [M/H]<-0.7. Possible discrepancies at higher metallicity, in the
upper part of the RGB, need to be confirmed with further observational data and
by extending all the models to the most metal rich regime. The SGB shape has
been used to set an upper limit to the cluster age, and consequently a lower
limit on the cluster distance. A discussion on the still open problem of the
mismatch between the observed and theoretical RGB bump location is also
presented.
