  CO emission, tracing the molecular content and distribution in galaxies, is a
privileged tool to trace gas towards the nucleus, since the HI tracer is in
general depleted there. A review is done of recent CO line observations, with
sufficient spatial resolution to indicate the morphology and kinematics of the
gas near the nucleus. The puzzling result that nuclei presently observed in an
active phase have little sign of fueling, is discussed.
