  We are carrying out a multi-purpose program of high signal to noise optical
spectroscopy at medium resolution of 30 BL Lac objects. Here we report the
detection of three new redshifts, and the discovery of three misclassified
sources. The new redshifts refer to PKS0754+100 (z=0.266), H-1914-194 (z=0.137)
and
  1ES0715-259, for which we derive a redshift of z=0.465 and also a ``new''
classification a Steep Spectrum Radio Quasar. In two cases (UM493 and 1620+103)
stellar spectra indicate a wrong classification. The three sources with new
redshift measurement show strong [OIII] emission in their spectra and their
host galaxy properties are known.
  The central black hole masses derived using the M_{BH}-L_{bulge} and the
M_{BH}-\sigma([OIII]) relations are compared.
