We investigate the influence of the finite Alfv6n velocity on the evolution of an active region filament. In general, variations of a current result in variations of the magnetic fields which spread around with the Alfvdn velocity. As a consequence of the fact that a magnetic field can only change with the Alfv6n velocity, a filament will experience the photospheric boundary conditions as these were at an Alfv6n travel time back in time. The inclusion of this retardation effect in the momentum equation of a filament leads effectively to an extra force term. This force contribution acts in the direction in which the filament moves and has therefore a destabilizing effect on the filament. Because a moving filament acts as an antenna of Alfv6n waves, the filament loses energy by the emission process. This leads to a radiative damping term in the equation of motion of the filament. In general, the radiative damping will be sufficiently strong to counteract the retardation instability. Numerical simulations show that during the energy build-up phase a filament follows the van Tend-Kuperus equilibrium curve. After the van Tend-Kuperus equilibrium has disappeared the filament goes through a transient phase moving with a sub-Alfv6nic velocity upward. At greater heights the repulsive Lorentz force of the photospheric surface current magnetic field is balanced by the radiative damping, resulting in a decreasing filament velocity. * Parts of this paper were presented at the 4th CESRA Workshop in Ouranopolis (Greece) in 1991.