We present new theoretical evaluations of optical and near-IR Surface Brightness Fluctuations ( SBF ) magnitudes for single-burst stellar populations in the age range t = 5 - 15 Gyr and metallicity from Z _ { \hbox { $ \odot$ } } / 200 to 2 Z _ { \hbox { $ \odot$ } } .
Our theoretical predictions can be successfully used to derive reliable distance evaluations .
They also appear to be a new and valuable tool to trace the properties of unresolved stellar populations .