  In this contribution two papers on the BL Lac object PKS 2155-304 are
presented. They are based on our program of systematic intensive optical
monitoring in search of fast variability events. In the first paper the results
of a CCD photometric campaign conducted at ESO (La Silla, Chile) on 6-14 July
1998, for a total time on the source of ~30 hours. Some peculiarities in the
light and colour cutves were evidenced. In the second paper we report on linear
polarization, as observed in the UBVRI bands in June and August 1998 for a
total of ~45 hours. Between the two epochs, the linear polarization in the V
band increased from ~3.5% to ~5.5%, and the position angle decreased from 100
deg to 70 deg. Significant day-to-day variations of both quantities are also
observed. An isolated "dip" of the polarization percentage occurred between 17
and 19 June in all bands: a decrease and subsequent rise of a factor of 2 is
seen in the linear polarization, accompanied by a variation of the position
angle by 90 deg.
