We present results from CCD UBVI photometric observations down to V = 19 mag and polarimetric observations down to V = 13 mag in the open cluster Trumpler 21. This cluster is interesting because it is located near the supernova remnant SNR G307.6-03 but the reality of any physical connection between them is far to be clear.

According with our analysis the cluster distance is d = 1400 pc. (Vo-Mv=10.7), has a mean color excess E(B-V) = 0.25 and its age is between 25 and 30x10⁶ years. From the polarimetric study, we could see that the polarization in this direction is about 1% and almost parallel to the galactic plane. We have also calculated the mass function slope.