  Although it is clear that the circumnuclear regions of galaxies are
intimately related to their host galaxies, most directly through their bars, it
remains unclear what exactly initiates and fuels nuclear stellar (starburst)
and non-stellar (AGN) activity. Deviations from axisymmetry in the
gravitational potential of a galaxy, set up by a bar or an interaction, are
known to cause gas inflow, and must at some scale and level be related to the
fueling of AGN and starbursts. We review the observed relations between bars
and interactions on the one, and nuclear activity of the Seyfert and starburst
variety on the other hand, and conclude that none of these relations is
particularly significant in a statistical sense, except in extreme and rare
cases, such as ultra-luminous infrared galaxies. Nuclear rings of star
formation, however, are not only related directly to non-axisymmetries in the
potential, but also, it seems, to the occurrence of nuclear activity. Their
role as potential tracers of the fueling process must be further explored.
