  I review the Globular Cluster Luminosity Function (GCLF) with emphasis on
recent observational data and theoretical progress. As is well known, the
turn-over magnitude (TOM) is a good distance indicator for early-type galaxies
within the limits set by data quality and sufficient number of objects. A
comparison with distances derived from surface brightness fluctuations with the
available TOMs in the V-band reveals, however, many discrepant cases. These
cases often violate the condition that the TOM should only be used as a
distance indicator in old globular cluster systems. The existence of
intermediate age-populations in early-type galaxies likely is the cause of many
of these discrepancies. The connection between the luminosity functions of
young and old cluster systems is discussed on the basis of modelling the
dynamical evolution of cluster systems. Finally, I briefly present the current
ideas of why such a universal structure as the GCLF exists.
