  We discuss a method to build up and study a sample of distant galaxies, with
2<z<5, using the gravitational amplification effect in cluster-lenses for which
the mass distribution is well known. The candidates are selected close to the
critical lines at high-z, through photometric redshift estimates on a large
wavelength range. With respect to other methods, this procedure allows to
reduce the selection biases in luminosity, thanks to the cluster magnification
of ~1 magnitude, and towards active SFRs when the near-IR domain is included.
Some new results obtained with this technique are presented and discussed.
