  We believe that the radiation we receive from Gamma-Ray Bursts (GRBs) and
radio loud Active Galacti Nuclei (AGNs) originates from the transformation of
bulk relativistic motion into random energy. Mechanisms to produce, collimate
and accelerates the jets in these sources are uncertain, and it may be fruitful
to compare the characteristics of both class of sources in search of
enlightening similarities. I will present some general characteristics of radio
loud AGNs and GRBs such as their bulk Lorentz factors and the power of their
jets. I will also discuss the way in which the energy in bulk relativistic
motion can be transformed into beamed radiation, and consider the possibility
that both classes of sources can work in the same way, namely by an
intermittent release of relativistic plasma at the base of the jet: shells
ejected with slightly different velocities collide at some distance from the
central engine, dissipating part of their kinetic energy, and keeping the rest
to power the extended radio lobes (in AGNs) or to produce the afterglow (in
GRBs).
