  We have observed the QSO 3C345 with VSOP at 1.6GHz and 5GHz and with the VLBA
at 22GHz and 43GHz, with 24 epochs in total, from 1997.40 to 1999.69. This
study, combined with previous observations, reveals periodic changes in the
parsec-scale jet. This quasi-periodicity can be found in the initial position
angles, the trajectories and the flux density evolution of the jet components,
with a period of about 9 years. This period should reflect the dynamics of the
material in the central region of 3C345 and it is possibly related to a
putative binary black hole in the center of this object.
