  The study of the optical continuum of radio galaxies shows that about 30%
have a young stellar population component. Among them are the most far-IR
bright radio galaxies. A further indication of the relatively gas rich
environment of these galaxies (possibly related to the recent merger from which
they originate) is the high fraction being detected in HI. Here we present
recent results obtained from the study of neutral hydrogen (detected either in
emission or absorption) in a group of starburst radio galaxies. In some
objects, large-scale (tens of kpc) structures involving HI masses exceeding
10^9 M_sun are observed. In these cases, the HI can be used to study the origin
and evolution of these systems and the timescales involved. In this respect,
the parameters obtained from the study of the stellar populations and from the
HI can be complementary. In other objects, very broad (> 1000 km/s), mostly
blueshifted HI is detected in absorption. This result shows that, despite the
extremely energetic phenomena occurring near an AGN - including the powerful
radio jet - some of the outflowing gas remains, or becomes again, neutral. This
can give new and important insights in the physical conditions of the gaseous
medium around an AGN. The possible origin of the extreme kinematics is
discussed.

Astrophysics