  The study of both neutral and ionized gas in young radio sources is providing
key information on the effect the radio plasma has on the ISM of these objects.
We present results obtained for the compact radio sources PKS1549-79, 4C12.50
and PKS1814-63 and for the intermediate-size radio galaxy 3C459. At least in
the first two, low ionisation optical emission lines and HI absorption appear
to be associated with the extended, but relatively quiescent, dusty cocoon
surrounding the nucleus. The [OIII] lines are, on the other hand, mostly
associated with the region of interaction between the radio plasma and the ISM,
indicating a fast outflow from the canter. A case of fast outflow (up to ~1000
km/s) is also observed in HI in the radio source 4C12.50. As the radio source
evolves, any obscuring material along the radio axis is swept aside until,
eventually, cavities (of the same kind as observed e.g. in Cygnus A) are
hollowed out on either side of the nucleus. We may witness this phase in the
evolution of a radio source in the radio galaxy 3C459.
