  We review the most outstanding issues related to the study of the morphology
of the Horizontal Branch (HB) in the Color-Magnitude Diagrams of Galactic
Globular Clusters and its use as age indicator. It is definitely demonstrated
(see also Bolte, this meeting) that age cannot be the only 2nd-P driving the HB
morphology. Other candidate 2nd-Ps are briefly examined, with special attention
to the possible influence of cluster stellar density.
