The superluminal quasar 3C345 has a curved, one-sided jet-like radio structure1,2. Ejected material has been observed travelling at apparent speeds of 13–17c (ref. 3). We report here new observations at 22 GHz which show that the most recently ejected component4 is not moving radially away from the compact radio core, but along a trajectory which could be interpreted as either a curved path originating in the compact core, or a straight line, in which case the origin of ejection is not coincident with the compact radio core. The observations provide evidence of acceleration of this component. © 1983 Nature Publishing Group.