Seyfert galaxies with linear nuclear radio structures have been studied with long-slit spectroscopy. Very extended, narrow [OIll] emission is detected in several of the objects, highly elongated along the radio source axis. This Extended Narrow Line Region would be consistent with interstellar gas that is photoionized by collimated energetic radiation from the nucleus. Within the Narrow Line Region detailed correspondences between [Olll] emission features and individual radio components have been found in a number of Seyfert galaxies. Velocities and positions of these [OIll] features suggest that they may be produced when ambient gas has been compressed by an outmoving radio component, subsequently cools down behind the bow shock and then is photoionized by the nuclear continuum source.
Jets of extragalactic radio sources in many cases show signs of precessional motion. This may arise when two massive compact objects are close to each other within a galaxy nucleus. The observed radio brightness distributions are modelled by slowly precessing jets, often relativistic. Interesting illustrations of their behaviour are offered by the frequency of occurrence of one-sided jets and by an explanation of the "preferential avoidance'' effect. There may be some evidence for a binary massive black hole in the nearest galaxy nucleus, the Galactic Centre.