  By summing a large number of ROSAT High Resolution Imager (HRI) observations
of the variable radio galaxy 3C 390.3, we demonstrate that the X-ray emission
associated with the northern radio lobe (reported by Prieto 1997) can be
identified with hotspot B. None of the other hotspots have been detected. We
present evidence that the anomalous X-ray emission is the consequence of a
strong shock produced where the northern radio jet impinges onto an external
galaxy.
