  We report on our optical monitoring of the BL Lac object S5 1803+78 from 1996
to 2011. The source showed no clear periodicity, but a time scale of about 1300
days between major flares is possibly present. No systematic trend of the color
index with flux variations is evident, at variance with other BL Lacs. In one
flare, however, the source was bluer in the rising phase and redder in the
falling one.
  Two Gamma-ray flares were detected by Fermi-GST during our monitoring: on the
occasion of only one of them we found simultaneous optical brightening. A
one-zone Synchrotron Self Compton (SSC) model appears too simple to explain the
source behavior.
