  We present CCD BVI photometry of the old open cluster Berkeley 21, one of the
most distant clusters in the Galactic anticentre direction, and possibly the
lowest metallicity object in the open clusters sample. Its position and metal
abundance make it very important for the study of the Galactic disc. Using the
synthetic Colour - Magnitude Diagram method, we estimate values for distance
modulus (m-M)0=13.4-13.6, reddening E(B-V)=0.74-0.78 (with possible
differential absorption), and age=2.2-2.5 Gyr.
