A study of the relaxation phenomenon in polystyrene networks containing linear polystyrene chains of high molecular weight has been carried out using measurements in methylcyclohexane and in the dry state by dynamic sinusoidal deformation and static stress relaxation. It is shown that the relaxation of the free chains contained in the network is (i) proportional to (1 − v 2 2) where v 2 is the volume fraction of the crosslinked network in the dry state, and (ii) depends very little on their concentration in the network. The distribution of relaxation time shows a peak related to the glass transition of the networks and a second peak corresponding to the spectrum of the linear chains of high molecular weight.