  We report redshift measurements for 12 BL Lacertae objects from a program
aimed at obtaining high signal to noise (up to ~ 500) optical spectroscopy of a
mixed sample of objects. The new observations, gathered with the 8 m ESO Very
Large Telescope, allowed us to detect weak spectral features down to a line
equivalent width as small as ~ 1 Angstrom. The new redshifts fall in the
0.2-1.3 interval. For nine objects we observe emission lines from the active
nucleus. In the remaining three cases absorption lines from the host galaxy are
found. For two objects we also detect absorption lines from intervening
systems.
