  A sample of 8 QSOs with 1.7 < z_em < 3.7 has been observed with VLT/UVES at a
typical resolution 45000 and S/N~40-50. Thanks to the two-arm design of the
spectrograph, a remarkable efficiency has been achieved below 400nm and above
800nm, which translates immediately in the possibility of obtaining new
results, especially at z<2.5. We report here new insight gained about the
evolution of the number density of Ly-a lines, their column density
distribution, the ionizing UV background and the cosmic baryon density.
