A detailed study of the Star Formation History of the Sgr dSph galaxy is performed through the analysis of the data from the Sagittarius Dwarf Galaxy Survey ( SDGS ; Bellazzini , Ferraro & Buonanno 1999 ) .
Accurate statistical decontamination of the SDGS Color - Magnitude diagrams allow us to obtain many useful constraints on the age and metal content of the Sgr stellar populations in three different region of the galaxy .

A coarse metallicity distribution of Sgr stars is derived , ranging from [ Fe / H ] \sim - 2.0 to [ Fe / H ] \sim - 0.7 , the upper limit being somewhat higher in the central region of the galaxy .
A qualitative global fit to all the observed CMD features is attempted , and a general scheme for the Star Formation History of the Sgr dSph is derived .
According to this scheme , star formation began at very early time from a low metal content Inter Stellar Medium and lasted for several Gyr , coupled with progressive chemical enrichment .
The Star Formation Rate ( SFR ) had a peak from 8 to 10 gyr ago when the mean metallicity was in the range -1.3 \leq [ Fe / H ] \leq - 0.7 .
After that maximum , the SFR rapidly decreased and very low rate star formation took place until \sim 1 - 0.5 Gyr ago .